In a five-minute appearance in the White House Rose Garden, Mr. Bush fulfilled a major campaign promise by formally announcing the withdrawal, which will free the Pentagon to test and deploy a missile defense without restrictions.

He maintained that his move would at once rid the United States of a relic of the Cold War and force the United States and Russia to find a way to replace it.

"I have concluded the ABM treaty hinders our government's ability to develop ways to protect our people from future terrorist or rogue-state missile attacks," the president said Thursday.

Just hours before, he called President Jiang Zemin of China and offered to hold "high-level strategic talks," according to senior administration officials. Mr. Jiang, who had earlier warned that abandoning the ABM treaty would trigger an arms race in Asia, agreed to begin the talks soon, the officials said.

In Moscow, President Vladimir Putin called Mr. Bush's decision "mistaken" in an appearance on state-run television. He said that he had repeatedly refused American entreaties for "a common withdrawal" from the treaty and had tried to preserve it.

But Mr. Putin's statement was so mildly worded and so focused on preserving the relationship he has built with Washington over the past six months that White House officials insisted the withdrawal would amount to a blip in American relations with Russia.

Particularly since agreeing to join the war on terrorism, Mr. Putin has seen Washington mute its criticism of Russia's conduct in Chechnya and open up cooperation with the North Atlantic Treaty Organization and entry into the World Trade Organization. The Russian leader seems anxious to preserve those gains while bowing to the inevitable.

Mr. Putin asserted that even after reducing Russia's missile fleet to 1,500 to 2,200 intercontinental missiles - about the range Mr. Bush plans for America's arsenal - Russia would be able to overwhelm whatever anti-missile system the Pentagon deploys.

On Thursday, Mr. Bush took no questions about how he reached one of the most momentous presidential decisions in the half-century history of arms control agreements, though one he has telegraphed for months.

"Defending the American people is my highest priority as commander-in-chief, and I cannot and will not allow the United States to remain in a treaty that prevents us from developing effective defenses," he said. Then he turned and walked briskly back to the Oval Office.

Reaction to Mr. Bush's decision was both swift and predictable.

Conservatives in the president's own party rejoiced. In just a year, the Republicans have achieved two of their major goals, a tax cut and abandonment of the ABM treaty. Democrats and enthusiasts of strategic arms treaties were withering in their accusations that the president, in pursuit of an unproven technology, was running the risk of triggering an arms race.

"A year ago, it was widely reported that our intelligence community had concluded that pulling out of ABM would prompt the Chinese to increase their nuclear arsenal 10-fold, beyond the modernization they are doing anyway," said Senator Joseph Biden, Democrat of Delaware, the chairman of the Senate Foreign Relations Committee.

"And when they build up, so will the Indians, and when the Indians do, so will the Pakistanis. And for what? A system no one is convinced will work."

Mr. Bush called Mr. Jiang on Thursday, in part to address China's concerns about the decision, officials said. While Russia's nuclear security is little affected by the anti-missile program, Beijing possesses only 20 or so nuclear missiles capable of reaching the United States.

That means its ability to launch an attack could well be neutralized by an anti-missile system, if one is successfully developed.

White House officials refused on Thursday to reveal the substance of Mr. Bush's discussion with Mr. Jiang, but senior officials said the offer of talks was intended to make sure that China did not feel that it was being frozen out as Washington builds a "strategic framework" with Russia.

Mr. Putin's reaction appeared loosely coordinated with the White House; Mr. Bush called him a week ago to warn of an impending announcement, and ever since the two capitals have been exchanging drafts of their statements.

Mr. Putin made it clear that he had a wider agenda, and that he did not plan to dwell on Mr. Bush's decision. While he failed to persuade Mr. Bush to retain the treaty, he has gotten much of what he needs from Washington.

As a senior administration official said: "it's not like Putin is going home empty handed." China Stresses Global 'Stability'

China's president, Mr. Jiang, has called for multilateral efforts to ensure global stability following the U.S. decision to abandon the ABM treaty and press ahead with a missile defense system, Reuters reported from Beijing.

"China is willing to work with other countries to make efforts to safeguard world peace and stability," Chinese news organizations quoted him on Friday as saying.

"Under the current situation, it is very important to safeguard the international arms control and disarmament system," Mr. Jiang said after conversations with Mr. Bush and Mr. Putin.