More than three years after the most deadly attack on our country, the threat of international terrorism is greater than ever before. Osama bin Laden remains on the loose. Sleeper cells continue to recruit and operate in the United States. And nearly 18,000 al Qaeda militants have expanded their presence to 60 countries across the globe.

The Bush administration likes to claim that three-quarters of

al Qaeda’s leadership have been killed or captured — a nice factoid if true, but a wholly inadequate measure of our progress in the war on terror. In a world where 19 hijackers armed with boxcutters murdered more than 3,000 Americans, a better measure of our security is

not the number of terrorists but the likelihood that one terrorist or terrorist cell will obtain deadly weapons and the capability to use them on American soil.

The most urgent threat is a nuclear weapon in the hands of terrorists. Only 100 pounds of highly enriched uranium could make a crude nuclear bomb that would leave thousands dead. Osama bin Laden has made clear his desire to develop and acquire nuclear weapons. His goal: to kill 4 million Americans with the press of a button.

The technology to produce a nuclear bomb is easier to obtain than we might like to believe. Earlier this year, a Pakistani scientist named A.Q. Khan confessed to operating a global black market for nuclear technology. The head of the International Atomic Energy Agency, Mohamed ElBaradei, called it a “veritable nuclear Wal-Mart.”

Fissile material — the ingredients necessary to make a nuclear bomb — is in abundant supply around the world. Highly enriched uranium is used to fuel more than 100 research reactors in dozens of countries. Many of these are academic or industrial facilities that have no more security than a night watchman and a chain link fence.

Russia alone has more than 1,000 metric tons of military HEU and 150 metric tons of military plutonium from dismantled nuclear weapons. Efforts to dispose of some of this material have all but stalled, and security upgrades have been completed for only 22 percent of Russia’s nearly 600 tons of nuclear bomb material.

The only real solution to this threat is to prevent terrorists from obtaining nuclear weapons or the materials necessary to make them in the first place. The Bush administration has failed to make this a priority.

In fact, the amount of nuclear material secured in the two years after the Sept. 11, 2001, attacks was less than the amount secured in the two years prior. Funding for the Cooperative Threat Reduction Initiative — the joint United States-Russia program to secure and dismantle nuclear weapons — has gone virtually unchanged. At current funding rates, it will take 13 years to secure Russia’s fissile material.

A striking example of the Bush administration’s failure to prioritize the safeguarding of weapons materials was the recent disclosure by the IAEA that nearly 380 tons of conventional weapons have gone missing from the al Qaqaa military facility in Iraq. More than half of it was HMX, a high-grade explosive that can be used to detonate a nuclear weapon. Less than a pound of a similar material brought down the PanAm 103 flight that killed more than 250 passengers and crewmembers over Lockerbie, Scotland.

Bogged down in Iraq, the administration has also allowed rogue nations to slide closer toward nuclear capability. North Korea continues to defy the international community by reprocessing enough plutonium to create six nuclear bombs. The administration ignored Iran’s proliferation and was absent from the diplomatic effort that persuaded Iran to stop reprocessing uranium. And we have learned recently that even Brazil is refusing to allow IAEA inspections of its new Resende nuclear power facility, which studies claim will have the potential to build six nuclear weapons per year.

Our nation needs a comprehensive strategy to secure and eliminate the world’s fissile material. The following is a multipoint blueprint to achieve those goals:

• Our first priority for controlling fissile material must be installing strong and committed leadership at the top of our nonproliferation institutions. The president should start by nominating a new Energy secretary committed to pursuing an aggressive nonproliferation agenda and capable of following through with the administration’s Global Threat Reduction Initiative. Congress can show its leadership by establishing a Cabinet-level director of nonproliferation with full budgetary authority over our nonproliferation programs to develop a strategic plan to counter the threat of weapons of mass destruction.

Reps. Ellen Tauscher (D-Calif.), John Spratt (D-S.C.) and I have already introduced a bill to do this.

• We need to devote more resources to securing nuclear weapons material, both at home and abroad. Funding for the Cooperative Threat Reduction Initiative must be increased, and burdensome regulations must be lifted. We simply can’t wait 13 years to safeguard these materials.

• We need to show the world our commitment to international nonproliferation agreements. We must sign and ratify the Fissile Material Cut-Off Treaty to end global production of fissile materials. Any agreement should include real verification mechanisms. We also need to remain true to our current commitments through the Nonproliferation Treaty — efforts to develop and test new nuclear weapons, including the so-called Robust Nuclear Earth Penetrator, are dangerous and unnecessary. Additionally, we need to work with the international community to close a loophole in the Nonproliferation Treaty, which has allowed rogue nations like Iran and North Korea to continue to enrich uranium and reprocess plutonium under the guise of a nuclear power program.

• We need to renew our pledge with the former Soviet Union to secure and reduce our nuclear stockpile. The United States has 10,000 nuclear weapons in its stockpile, more than half of which are on high alert status; Russia has 17,000, just under half of which are active. Under current obligations, both countries will reduce their stockpiles to roughly 2,000 nuclear weapons by 2012. That could be too late.

• Finally, we need to do more at home to protect our nation’s infrastructure from the threat of weapons of mass destruction. We need to invest more in fencing, surveillance, and security guards for our nation’s infrastructure and mass transit systems.

When the 9/11 commission released its report, its instructions to Congress were clear. The United States must redouble its commitment to countering the threat of proliferation, or face the dire consequences. Al Qaeda has been seeking the materials to make a nuclear weapon for 10 years and views the acquisition of weapons of mass destruction as a “religious obligation.”

The best strategy to win the war on terror is to cut off the threat at the source — by removing and securing the world’s fissile material.

Rep. Marty Meehan (D-Mass.) is ranking member of the Armed Services terrorism and unconventional threats subcommittee and sits on the Judiciary subcommittee on crime, terrorism and homeland security.