By emphasizing its option to withdraw from the 1972 Anti-Ballistic Missile treaty, the Bush administration is indicating that it is prepared to endure a firestorm of criticism — from Russia, from U.S. allies and from Congress — for going it alone on missile defense.

The administration says it still hopes to reach an accommodation with the Russians that would "set aside" the treaty -- presumably replacing it with some other arrangement that permits the United States to develop and deploy the kind of missile defenses President Bush says are urgently needed.

In that case, the administration probably could proceed without fierce opposition from the allies.

But if that cannot be done, and if Bush sticks to his promise of building a robust missile defense, then the likely choice given recent comments from Bush aides would be to exercise a provision in the ABM treaty which permits either party to withdraw on six months' notice.

The question is how long Bush would be willing to wait on the Russians. It's also unclear whether Bush, if faced with the decision, would actually withdraw from a treaty that many key U.S. allies, including Germany and France, are reluctant to abandon as long as the Russians insist it remain in force.

Jan Lodal, an arms control expert who was a deputy under secretary of defense during the Clinton administration, said the United States has never withdrawn from an arms control treaty. He thinks it would be a mistake to exercise that option anytime soon, since the Pentagon could adjust its anti-missile technology testing program for 2002 to avoid any appearance of conflict with the ABM treaty.

"We don't have any compelling reasons" to withdraw as early as next year, Lodal said in an interview.

The withdrawal option has been there all along, of course, and Bush aides have mentioned it from time to time. But in recent days several administration officials have emphasized the possibility of withdrawing, perhaps in hopes of increasing pressure on the Russians to strike a deal soon.

John Bolton, the under secretary of state for arms control, said in an interview with Echo of Moscow radio station on Tuesday that the United States is prepared to unilaterally withdraw from the ABM treaty if necessary. He mentioned this in the context of a planned November meeting in Texas between Bush and Russian President Vladimir Putin, leading some to conclude that Bolton was signaling that if no deal were reached by then, the United States would feel compelled to withdraw.

On Wednesday Bolton said there is no such deadline.

Russia is opposed to abandoning the treaty, which it calls a cornerstone of international security. But Bush says it is a relic of the Cold War and does not reflect the security threats of the 21st century, such as ballistic missiles in the hands of nations like North Korea which are hostile to the United States.

The Bush administration proposed that both countries jointly withdraw from the treaty, but the Russians rejected that approach when it was presented by Defense Secretary Donald H. Rumsfeld in Moscow on Aug. 13.

After Rumsfeld's return to Washington, he and his aides began stating more explicitly in public the option of withdrawing from the treaty — an option they had mentioned but not emphasized earlier.

In an Aug. 17 interview with PBS Newshour, Rumsfeld was asked to respond to comments by Russian officials that if the United States violated or abandoned the treaty, then Russia might feel compelled to add multiple nuclear warheads to missiles in its arsenal which currently have single warheads.

"If we are unable to establish a new relationship with Russia so that we can get the treaty behind us ... then obviously the United States would have to give notice" of its intent to withdraw, Rumsfeld said.

Three days earlier, he made a similar remark in an interview with KSDK-TV in St. Louis, while adding that if the United States withdrew from the treaty, it would continue talking with the Russian government about establishing a new security relationship.