For decades, the Soviet nuclear threat cast an ominous cloud over life in this country. The dual-superpower world of those days provided a frightening enemy but also a strange stability. Given our mutual power to annihilate one another, neither side proved ready to undertake a risky attack.

But those days are over. Rogue regimes – some of them state sponsors of terror – are using clandestine methods to develop the world’s most dangerous weapons. Meanwhile, radical groups are seeking resources and technology to create nuclear arms of their own. And there is no telling what such groups or states will do once they have harnessed such horribly destructive power.

Some of these networks have even scoured former Soviet republics, hoping to harvest some of the nuclear materials that remain there. And a handful of governments apparently think that acquiring nuclear weapons will immediately propel them to superpower status, regardless of how they treat their people or deal with the rest of the world.

These widespread and often hidden threats represent our challenge today. The notion of nonproliferation is no longer the static idea that two rival superpowers must stand down from the brink. It is instead a very complex and dynamic problem with several potential and unstable hotspots around the globe. In short, nonproliferation, traditionally synonymous with “patience,” must be transformed into proactive policymaking.

Nowhere is this mantra more imperative than vis á vis Iran, whose potential for developing nuclear weapons could destabilize the entire Middle East. The current regime in Tehran has proved disgraceful and dangerous in ways that call for action, not just rhetoric. Iran has sponsored and armed terror agents around the world. It has engaged in systematic attempts to destabilize Iraq and counteract our efforts there.

Tehran has undermined the Lebanese government and Palestinian President Mahmoud Abbas through its support for the terrorist groups Hamas and Hezbollah. It has provoked fears in the Arab world that it aims to spearhead Shiite Islamist hegemony across the Middle East. It insists that Israel has no right to exist. And Iran’s president denies the very fact of the Holocaust. As a witness to that horror myself, I find this last outrageous assertion particularly appalling.

Many members of Congress and the administration have expressed outrage over the words and deeds emanating from Tehran. But as Iran’s plans for nuclear weapons development have been laid bare through inspections and intelligence, very little has been done.

So I am proposing a bill, the “International Nuclear Fuel for Peace and Nonproliferation Act,” that would call Iran’s bluff on its supposedly peaceful nuclear energy program. The legislation would lend United States backing and resources to the creation of an international fuel bank. Countries that agree not to engage in uranium enrichment and spent-fuel reprocessing – telltale signs of weapons development – would receive assurances of a steady and reliable supply of nuclear fuel from this international fuel bank.

If a nation agrees to participate in this system and accept its requirements, it proves that its nuclear goals are strictly for civilian energy production, not for nuclear weapons. So if Tehran is true to its word, it would welcome the chance to secure a stable supply of nuclear fuel and halt its enrichment activities. If it declines the offer, its military intentions will be exposed for all to see.

We intend to mark up this important measure in this committee on May 23, and I look forward to the support of my colleagues on both sides of the aisle. One of the most ardent supporters of such a measure, the former distinguished Senator Sam Nunn, is with us today. His organization, The Nuclear Threat Initiative, has made a pledge of $50 million, backed by Warren Buffett, to foster the creation of a nuclear fuel bank.

This bill is not the only tough measure we can take to stop Iran from “going nuclear.” I also urge the Administration to take a tougher tact. And I encourage members to support another piece of legislation I have introduced that would strengthen export and import sanctions on Iran and penalize companies here and abroad doing business with its energy program.

Iran is not the only country where we must halt the spread of nuclear weapons technology. North Korea remains the other major threat, as it continues to stall and engage in double-talk over their commitments. The United States, with the crucial help of China, must use the framework of the Six-Party Talks to pressure the North Korean regime to completely de-nuclearize. Anything short of total nuclear disarmament there will be considered failure.

Finally, the emerging menace of non-state actors poses perhaps the biggest challenge to the nonproliferation regime since the Nuclear Nonproliferation Treaty was opened for signature in 1968. Dangerous and unscrupulous scientists like the Pakistani nuclear expert A.Q. Khan concern all rational people as much as either the president of Iran or North Korea. The United States and its allies have to make sure that all nations root out any A.Q. Khan copycats before they put nuclear technology in the hands of groups which have no qualms about wiping out thousands or millions of people.

Indeed, the ghastly attacks of 9/11 jolted us into realizing just how small the world is, that terrorists can reach any of us. It also reminded us that the chilling possibility of nuclear attack no longer centers on Moscow. It is concerned with a nameless, morphing threat. And so we cannot just talk tough about these groups and about rogue regimes that sponsor them or harbor their own nuclear ambitions. We must leverage the vast tools and resources of the United States to stop them cold.