With polls showing that John McCain holds a big lead on foreign policy readiness, and with McCain constantly arguing that Obama would surrender in the war on terror, one of Obama's chief political challenges is to drive home the message that his national security policies constitute going on offense against global dangers.

Today Obama is trying to do just that, convening a "21st Century Threats" summit in Indiana with potential running mates Evan Bayh and Sam Nunn, as well as a bunch of foreign policy experts. Obama's speech -- part of his ongoing national security tour leading up to his visit abroad next week -- is underway.

According to Obama's prepared remarks, he'll make the case today that pulling out of Iraq and refocusing our resources in a wholly new way constitutes a real offensive against terrorism.

"It's time to update our national security strategy to stay one step ahead of the terrorists -- to see clearly the emerging threats of our young century, and to take action to make the American people more safe and secure," Obama will say. "Today, we will focus on nuclear, biological, and cyber threats -- three 21st century threats that have been neglected for the last eight years."

Obama will argue that we need to do more to secure the 50 tons of highly enriched uranium that's poorly secured around the world, and will also argue that we need to make eliminating all nukes a central policy goal. He'll also argue for the development of new technology to deal with bio-terror.

It's worth noting once again that Obama is staking his candidacy on the rather audacious belief that he can change, through persuasion, the way national security is discussed in this country -- that Dems don't have to cede this turf to the GOP.

Full prepared remarks after the jump.

Late Update: Steve Benen adds some choice thoughts, and much more context.

It's great to be back in Indiana with such a terrific group of experts. In a few moments, we'll open this up to a discussion, but first I'll make a few comments about some of the emerging threats that we face in the 21st century, and offer some ideas about how we can face those threats.

Throughout our history, America has confronted constantly evolving danger. From the oppression of an empire to the lawlessness of the frontier; from the bombs that fell on Pearl Harbor to the threat of nuclear annihilation - Americans have adapted to the threats posed by an ever-changing world.

For most of our history, the most significant danger to our security came from states. The physical safety of our people was protected by oceans. The national security of the United States was buttressed by our economic strength, and a powerful military that answered every call. Today, the dangers extend beyond states alone to transnational security threats that respect no borders. These are threats that can arise from any part of the globe and spread anywhere, including to our own shores - dangers like pandemic disease, nuclear weapons proliferation, environmental degradation, international criminal networks, and terrorism. Of course, we have long struggled against terrorism, and in the closing decades of the 20th century, we tragically lost American lives on our soil and abroad. But it was hard to change a mindset that saw the extremism, the resentment, the terrorist training camps, and the killers as distant threats in the dark corners of the world, far away from the American homeland.

Then, one Tuesday morning in 2001, everything changed. I remember hearing the news on my car radio in downtown in Chicago: a plane had hit the World Trade Center. By the time I got to my meeting, the second plane had hit, and we were told to evacuate. People gathered in the streets and looked up at the sky and the Sears Tower. We feared for our families and our country. We mourned the terrible loss suffered by our fellow citizens in those two office towers, at the Pentagon, and in a simple field in Pennsylvania. Back at my office, I watched the images from New York: a plane vanishing into glass and steel; men and women clinging to windowsills, then letting go; tall towers crumbling to dust. It seemed all of the misery and all of the evil in the world were in that rolling black cloud, blocking out the September sun.

What we saw that morning forced us to recognize that in a new world of threats, we are no longer protected by the size of oceans or solely by our military power. In a globalized world, the power to destroy can lie with individuals - not just states. The terrorists use a world of globalization to travel freely, to transfer money, to use telecommunications to carry out their plots. On 9/11, they used our open society to kill on a terrible scale, but even more terrifying was the thought that they could get their hands on the world's most deadly technology.

Since then, we have taken many steps to strengthen our defense. Some of the most visible address the attacks - or failed attacks - that have already taken place. So after 9/11, airline security tightened and plastic knives replaced metal ones. After the so-called shoe bomber, we started having our shoes screened. After a plot detected in London to ignite dangerous liquids, we started to check our gels and shampoos.

The danger, though, is that we are constantly fighting the last war - responding to the threats that have come to fruition, instead of staying one step ahead of the threats of the 21st century. This is what the 9/11 Commission called our "failure of imagination." And, after 9/11, nowhere was this more apparent than in our invasion of Iraq. Instead of adjusting to the stateless threats of the 21st century, we invaded and occupied a state that had no collaborative relationship with al Qaeda. Instead of taking aggressive steps to secure the world's most dangerous technology, we have spent almost a trillion dollars to occupy a country in the heart of the Middle East that no longer had any weapons of mass destruction.

It's time to update our national security strategy to stay one step ahead of the terrorists - to see clearly the emerging threats of our young century, and to take action to make the American people more safe and secure. It's time to look ahead -- at the dangers of today and tomorrow rather than those of yesterday. America cannot afford another president who doesn't understand the threats that confront us now and in the future.

Today, we will focus on nuclear, biological, and cyber threats - three 21st century threats that have been neglected for the last eight years. It's time to break out of Washington's conventional thinking that has failed to keep pace with unconventional threats. In doing so, we'll better ensure the safety of the American people, while building our capacity to deal with other challenges - from public health to privacy.

It starts with the gravest danger we face - nuclear terrorism. One of the terrible ironies of the Iraq War is that President Bush used concern over this threat to invade a country that had no nuclear weapons program. In the meantime, Pakistani scientist AQ Khan was spreading to hostile nations the technology to produce nuclear weapons and the warheads to deliver them. But the fact that the President misled us into a misguided war doesn't diminish the threat of a terrorist with a weapon of mass destruction - in fact, it has only increased it.

We used to worry about our nuclear stalemate with the Soviet Union. Now, we worry about 50 tons of highly enriched uranium - some of it poorly secured - at civilian nuclear facilities in over forty countries around the world. Now, we worry about the breakdown of a non-proliferation framework that was designed for the bipolar world of the Cold War. Now, we worry - most of all - about a rogue state or nuclear scientist transferring the world's deadliest weapons to the world's most dangerous people: terrorists who won't think twice about killing themselves and hundreds of thousands in Tel Aviv or Moscow, in London or New York. And yet, despite initiatives that cost billions of taxpayer dollars, we still don't have an adequate strategy for detecting nuclear and biological materials, a problem that's being discussed at hearings in Congress today.

We cannot wait any longer to protect the American people. I've made this a priority in the Senate, where I've worked with Indiana's own Republican Senator Dick Lugar to pass a law accelerating our pursuit of loose nuclear materials. And I'll lead a global effort to secure all loose nuclear materials around the world during my first term as President.

But we need to do much more. It's time to send a clear message to the world: America seeks a world with no nuclear weapons. As long as nuclear weapons exist, we'll retain a strong deterrent. But we'll make the goal of eliminating all nuclear weapons a central element in our nuclear policy. We'll negotiate with Russia to achieve deep reductions in both our nuclear arsenals and we'll work with other nuclear powers to reduce global stockpiles dramatically. We'll seek a verifiable global ban on the production of fissile material for weapons. And we'll work with the Senate to ratify the Comprehensive Test Ban Treaty and then seek its earliest possible entry into force.

By keeping our commitment under the Nuclear Non-Proliferation Treaty, we'll be in a better position to rally international support to bring pressure to bear on nations like North Korea and Iran that violate it. Both of these nations have a history of support for terror. Both should face strong and increasing sanctions if they refuse to verifiably abandon their illicit nuclear programs. And both demand sustained, aggressive, and direct diplomatic attention from the United States, and that's what I'll provide as President.

Just as we must guard against the spread of nuclear terrorism, it's time for a comprehensive effort to tackle bio-terror. We have still failed to solve the anthrax attacks that killed Americans on our soil in 2001. We know that al Qaeda was attempting to develop biological weapons in Afghanistan. And we know that the successful deployment of a biological weapon - whether it is sprayed into our cities or spread through our food supply - could kill tens of thousands of Americans and deal a crushing blow to our economy.

As President, I will launch an effort across our government to stay ahead of this threat. To prevent bio-terrorism, we need to invest in our analysis, enhance our information-sharing, and give our intelligence agencies the capacity to identify and interdict dangerous bio-weapons around the world. To strengthen our efforts with friends and partners, I've proposed a Shared Security Partnership that invests $5 billion over 3 years to forge an international intelligence and law enforcement infrastructure to take down terrorist networks.

Just as we step up our ability to prevent an attack, we must also bolster our capacity to protect against - and respond to - the threats that may come. When it comes to bio-terror, this can mean the difference between a contained incident and a catastrophe. That's why we need to invest in new vaccines, to reduce the risk posed by those who would use disease as a weapon. That's why we must develop the technology to detect attacks and to trace them to their origin, so that we can react in a timely fashion. And to care for our citizens who are infected, we must provide our public health system across the country with the surge capacity to confront a crisis.

Making these changes will do more than help us tackle bioterror - it will create new jobs, support a healthier population, and improve America's capability to respond to any major disaster. And just as we'll find additional benefits to our action against bio-terror, we can - and must - strengthen our cyber defenses in the 21st century.

Every American depends - directly or indirectly - on our system of information networks. They are increasingly the backbone of our economy and our infrastructure; our national security and our personal well-being. But it's no secret that terrorists could use our computer networks to deal us a crippling blow. We know that cyber-espionage and common crime is already on the rise. And yet while countries like China have been quick to recognize this change, for the last eight years we have been dragging our feet.

As President, I'll make cyber security the top priority that it should be in the 21st century. I'll declare our cyber-infrastructure a strategic asset, and appoint a National Cyber Advisor who will report directly to me. We'll coordinate efforts across the federal government, implement a truly national cyber-security policy, and tighten standards to secure information - from the networks that power the federal government, to the networks that you use in your personal lives.

To protect our national security, I'll bring together government, industry, and academia to determine the best ways to guard the infrastructure that supports our power. Fortunately, right here at Purdue we have one of the country's leading cyber programs. We need to prevent terrorists or spies from hacking into our national security networks. We need to build the capacity to identify, isolate, and respond to any cyber-attack. And we need to develop new standards for the cyber security that protects our most important infrastructure - from electrical grids to sewage systems; from air traffic control to our markets.

All of this will demand the greatest resource that America has - our people. In the Cold War, we didn't defeat the Soviets just because of the strength of our arms - we also did it because at the dawn of the atomic age and the onset of the space race, the smartest scientists and most innovative workforce was here in America. For the last few months, I've talked about how America's economic competitiveness depends on education. The same holds true for our security. If we're not investing in math and science education, our nation will fall behind. And if we're not educating the best and brightest scientists, engineers, and computer programmers here in the United States, we won't be able to keep America safe.

That is the task that lies before us. We must never let down our guard, nor suffer another failure of imagination. It's time for sustained and aggressive action - to take the offense against new dangers abroad, while shoring up our defenses at home. As President, I will call on the excellence and expertise of men and women like the people here today. And I will speak clearly and candidly with the American people about what can be done - what must be done - to protect our country and our communities. Now, I'd like to turn to an open discussion.