President Bush spelled out his vision for global missile defense in a speech Tuesday at the National Defense University in Washington.

He began by reflecting on the nature of the post-Cold War world.

"Today's Russia is not our enemy," he said, arguing that threats to U.S. security come primarily from smaller tyrannical states such as Iraq and North Korea. "In such a world, Cold War deterrence is no longer enough.

"We need a new framework that allows us to build missile defenses to counter the different threats of today's world," said Bush, who spoke with Russian President Vladimir Putin before announcing his plan.

He said he told the Russian leader he would like to meet with him soon. White House officials said they were exploring the possibility of a meeting somewhere in Europe during the president's travels in connection with a European Union summit June 15-16. "I told him I'd love to meet with him beforehand, to look him in the eye and let him know how sincere I am about achieving a new way of keeping the peace," Bush said.

Bush firmly rejected the doctrine of Mutual Assured Destruction — the strategy of basing security on the threat of nuclear counter-attack — that governed the Cold War nuclear dynamic. He said the U.S. must "work with allies and friends who wish to join with us" to "deter anyone who would contemplate" the use of nuclear, chemical, or biological arms.

The president also said the U.S. must move "beyond the constraints" of the Anti-Ballistic Missile (ABM) treaty signed in 1972 by the United States and the former Soviet Union, emphasizing that while the treaty has served its purpose, it now needs to be replaced and that a "new cooperative relationship" with Russia would enable both countries to move away from it.

Bush's remarks marked the start of an intensified campaign to convince America's European and Asian allies — as well as Russia, China and others hostile to the idea — that attacks by ballistic missiles can best be deterred by defenses rather than large offenses.

Bush did not announce a timetable for deployment, or a cost estimate.

Some Democrats reacted negatively to the president's remarks.

"We fear the president may be buying a lemon here. There has not been a shred of evidence that this works. We've got to ask some very tough questions," said Senate Minority Leader Tom Daschle.

"Congress must guard against allowing missile defense systems becoming the policy, allowing the technology, in effect, to develop its own psychology," said Rep. Neil Abercrombie, D-Hawaii, ranking Democrat on House Armed Services' research and development subcommittee. "There is gradually being created in the United States a burgeoning military and corporate apparatus dependent in large measure on missile defense to rationalize its existence."

Shortly before the speech, Defense Secretary Donald H. Rumsfeld told reporters at the Pentagon that the president was not ready to commit to specific nuclear cuts to accompany the new defense strategy.

"He believes, correctly, that the United States is going to be able to reduce the number of warheads, and he has not concluded specific numbers, nor have I. We are in the process of studying that," Rumsfeld said, appearing with Australian Defense Minister Peter Reith.

Bush discussed his emerging nuclear policy in telephone calls Monday to German Chancellor Gerhard Schroeder, French President Jacques Chirac, Canadian Prime Minister Jean Chretien and British Prime Minister Tony Blair, as well as Lord Robertson, the secretary-general of the North Atlantic Treaty Organization. He spoke with Japanese Prime Minister Junichiro Koizumi last Friday.

The European allies have been cool to the idea of a large-scale U.S. missile defense, knowing that the Russians view it as an attempt by the United States to establish absolute military dominance.

"The message to Russia is that the development of a missile-defense system — so we can think beyond the confines of the Cold War era — is the best way to preserve the peace," White House spokesman Ari Fleischer said.

"From the president's point of view, he views it as a question of leadership," Fleischer said. "He believes that if the United States leads and that we consult wisely, our allies and friends will find good reason to follow and to join with us."

Henry Cooper, who directed the Pentagon's missile-defense programs during the first Bush administration, said Monday he hoped Bush would press for deployment of at least a rudimentary U.S. missile defense by 2004.

One way the United States could field a limited defense quickly is to accelerate development of a Boeing 747 jet fitted with a laser capable of shooting down ballistic missiles during the boost phase of their ascent through the atmosphere. That program already is in the works, although on its current schedule the Air Force says it would not be ready for combat until 2007.

Russia is likely to be encouraged by Bush's interest in further reducing the number of nuclear weapons, since Putin has pushed for cuts well below the Clinton administration's threshold. Putin has expressed an interest in cooperating with European nations on a regional missile defense, but he strongly opposes a missile shield that would protect the United States.

— The Associated Press contributed to this report