President Bush and Russian President Vladimir Putin agreed Sunday to tie U.S. plans for building a missile defense shield to talks on reducing both nations' nuclear stockpiles.

The leaders expressed a shared desire to discuss both offensive and defensive options as a package.

"The two go hand in hand," Bush said at a news conference after their meeting on the sidelines of a global economic summit. He also said he wants a new accord to replace the 1972 Anti-Ballistic Missile Treaty.

Bush described himself and his Russian counterpart as "young leaders who are interested in forging a more peaceful world."

Putin, speaking through an interpreter, said the announcement on linking offensive and defense weapons was "unexpected," and cautioned that neither country is ready to discuss details.

"We're not ready at this time to talk about threshold limits or the numbers themselves. But a joint striving exists," Putin said.

Bush's national security adviser, Condoleezza Rice, will travel to Moscow from Kosovo on Tuesday to begin discussing what the Bush administration has described as a new security framework.

"We expect to move quickly," she told reporters. "We clearly want an aggressive schedule to see how quickly we may be able to sketch out an agreement."

Bush's stepped-up moves to build a missile defense shield -- which U.S. officials have said could violate the ABM treaty within months -- have divided U.S. allies in Europe and infuriated Russia.

Putin had said the United States did not adequately explain why it wants to scuttle the ABM treaty, which was meant to curtail the arms race through built-in vulnerability to nuclear attack.

Soon after he became president, Bush directed the Pentagon to consider further cuts in nuclear stockpiles, and has suggested he would be willing to go ahead with reductions without comparable cuts by Russia.

Moscow fears a U.S. missile defense system would prompt an arms race it could not afford, as well as disrupt international stability. Putin has sought to rally European opposition to the U.S. plan.

The United States has about 7,000 strategic nuclear weapons. Under the START II agreement with Russia, that number will fall to between 3,000 and 3,500. In 1997, President Clinton and President Boris Yeltsin agreed in principle that a follow-on treaty should drop the numbers to 2,000 to 2,500. Putin has suggested 1,500 warheads each would be adequate.

Putin said Bush shares with him a desire to "have large cuts in offensive arms, and together we are going to move forward in this direction."

Putin has said that if the United State dumps the ABM, Russia will tear up all other arms control agreements. He also has suggested that Moscow could respond to U.S. moves by fitting multiple warheads to its single warhead missiles.

Asked about that threat on Sunday, Putin said that if the new talks go well, "We might not ever need to look at that option, but it's one of our options."

Bush expressed hope that the United States and Russia would reach agreement. "We have agreed to find common ground if possible," Bush said. "I believe we'll come up with an accord. We'll work hard toward one."

In a joint statement, Bush and Putin said "major changes in the world" compelled them to link offensive and defensive measures. They said they had already found "strong and tangible" areas of agreement.

The two leaders also discussed the Kyoto global warming pact, which Bush opposes. Bush declined to answer whether the United States will present its new plan for reducing global warming at a fall international conference, saying only that U.S. officials were trying to develop an alternative strategy as quickly as possible.

Bush and Putin met inside the 16th century Palazzo Doria Spinola following their participation in the annual summit of the world's leading industrialized nations.

Sunday's meeting was their second session. The first came during an ice-breaking summit last month in Slovenia. During a gift exchange between the two leaders, Bush gave Putin a belt with the presidential seal. In return, he received a silver medallion with the Genoa summit logo on one side, and a picture of the Kremlin on the other.

They are to meet again at Bush's Texas ranch this fall, and during a conference on the Asia-Pacific region in Shanghai, China.