MOSCOW (AP) – Secretary of Defense Gates on Monday urged Russia to drop its opposition to American plans to develop defenses in Europe against long-range nuclear missiles, but the Russians refused to budge.

“We face new threats that require new strategies for deterrence and defense,” Mr. Gates said in a prepared statement delivered with Russian Defense Minister Anatoly Serdyukov seated beside him. “We invite Russia to join our defensive endeavor as a partner.”

Mr. Serdyukov, however, made clear that Moscow is opposed.

“The Russian position with respect to this issue remains unchanged,” Mr. Serdyukov said.

“We do believe that deploying all the strategic elements of the ballistic missile defenses is a destabilizing factor that may have a great impact upon global and regional security,” he added.

The Bush administration hopes a series of high-level meetings this week will yield the first sign of a crack in Russia’s opposition to a top-priority American defense project – building anti-missile bases in Poland and the Czech Republic.

The bases would be meant to provide protection in Europe from a long-range nuclear missile launched by Iran – a threat that American officials say may be fast approaching but that the Russians say is exaggerated.

The dispute has grown into a major irritant in American.-Russian relations.

Mr. Gates, on his first visit to Russia since taking office last December, was meeting Monday with Serdyukov, President Vladimir Putin and other senior officials, to gauge their initial reaction to a new set of American proposals designed to soften Russian objections.

“It’s nice that you accepted the invitation and that President Bush sent you so quickly,” Mr. Putin said. “We have planned a conversation with him after our meeting.”

Russian-American relations are very important, Mr. Gates said, adding, “There is a great deal we can accomplish together.”

The proposals, presented quietly last week in Moscow and at NATO headquarters in Belgium, include sharing data collected by American sensors to provide early warning of ballistic missile launches, cooperation on missile defense research, and joint testing of the building blocks of an anti-missile system, according to an administration official traveling with Mr. Gates. Two officials on the trip from Washington discussed the proposals on condition they not be identified because the talks had not yet begun.

One official acknowledged that previous American proposals for such cooperation had fizzled, and that it likely would take time and multiple meetings and consultations to see if the Russians will change their mind.

“I don’t think we expect to solve this problem on this trip or to get even a definitive answer from the Russians necessarily on this trip,” one official said. “I hope we get at least a preliminary response.”

Later this week Secretary of State Rice is due to attend a NATO meeting in Norway that is scheduled to include a session with Russian officials on the missile defense controversy and other issues.

The administration is consulting with Poland on hosting an American base with 10 missile interceptors, and is talking to the Czech government about hosting a radar system used to track hostile missiles in flight. Russia has long objected to a U.S. military presence on its periphery; Poland and the Czech Republic were part of the old Warsaw Pact that faced off against U.S.-led NATO during the Cold War.

Washington has repeatedly insisted that an anti-missile system in Europe would not threaten the viability of Russia’s vast offensive nuclear missile arsenal and would offer it some protection from a potential Iranian attack.

The Russians not only question the seriousness of the threat from long-range missiles, which American officials say is real and growing, but also the feasibility of American anti-missile technology as a response to any such threat.

Last week the Russian Interfax news agency quoted Sergei Ivanov, the first deputy prime minister and formerly the defense minister, as saying he saw “no grounds to talk about potential cooperation” on missile defense.

The Bush administration, however, sees the extension of its existing missile defense system to Europe as crucial.

“Whether Russia cooperates with us or not is really up to Russia. That’s a decision that they have to make,” one of the officials said. “Russia doesn’t get a veto over what we do” in missile defense.

Some of Russia’s opposition may be rooted in the history of the American missile defense program. It was famously jump-started with a 1983 “Star Wars” speech by President Ronald Reagan that envisioned a global shield against ballistic missiles, which Reagan hoped might one day lead to the abolishment of nuclear weapons. Leaders of the then-Soviet Union decried the Reagan idea, worked to enlarge European opposition to it and spent enormous sums building Soviet offensive missile capabilities to counter the American program. Some argue that the Soviet effort hastened the collapse of the Communist regime.

The American missile defense effort waned in the 1990s with the demise of the Cold War, and when it was revived in 2001 by the Bush administration it shifted its focus from Russia to North Korea and Iran.