President Bush says he wants to give Russia ample time to come to some sort of agreement on missile defense, but he makes clear he will not wait forever. Mr. Bush was asked about the missile defense controversy during a visit to Rome Monday where he met with Italian leaders and Pope John Paul II.

At the heart of the controversy is the 1972 Anti-Ballistic Missile Treaty. Russia says it bans development of missile defenses and is needed to prevent a new arms race. President Bush says the treaty is a relic of the Cold War and must be amended or replaced.

On Sunday, the two sides announced they will link discussion of defensive weapons to negotiations on reducing their stockpiles of offensive arms.

That doesn't mean Moscow is giving up its opposition to Mr. Bush's missile defense proposal, only that Russia has agreed to keep the dialogue going.

Mr. Bush said he knows the Russians have been operating under the ABM treaty for decades. He said he understands Russian President Vladimir Putin may need time to adjust to a new strategic framework. "His nation has been bound by that treaty. It's a treaty, of course, from which either party can withdraw with ample notice. And I understand why he wants time," Mr. Bush said.

But aides to Mr. Bush say he is talking about months, not years. And the president makes clear his patience has limits. He says time is of the essence. "Make no mistake about it: I think it's important to move beyond the ABM treaty," he said. "I would rather others come with us, but I feel so strongly and so passionately on the subject about how to keep the peace in the 21st century, that we'll move beyond, if need be."

The president's national security advisor, Condoleezza Rice, heads to Moscow Tuesday to start working on logistics for a new round of arms talks. She reinforced the President's message Monday, saying work on the missile defense system will continue regardless of what happens in discussions with Russia. She said at some point, as testing intensifies, the United States will be accused of violating the ABM treaty. "I would just draw your attention to the language which [says] just about anything that you test in an ABM mode that is not ground-based is, in fact, in violation of the treaty," she said. "So we're going to have to work at this with some urgency."

Ms. Rice says there is a certain sense of urgency within the Bush administration. She explained that the president knows he will, at most, have two terms in office. She said he wants to make sure the necessary technology is developed before his presidency is over.