MOSCOW — Responding to remarks by Defense Secretary Robert M. Gates, a top Russian diplomat said Thursday that Russia would not collaborate with the United States on missile defense unless Washington scrapped plans to deploy elements of the shield in Poland and the Czech Republic.

“We cannot partner in the creation of objects whose goal is to oppose the strategic deterrent forces of the Russian Federation,” said the Foreign Ministry spokesman, Andrei A. Nesterenko. “No one will do something that harms himself.”

“Only the United States’ rejection of plans to base in Europe the so-called third position area of the missile-defense shield could mark the beginning of a full-fledged dialogue on the question of cooperation and reaction to likely missile risk,” Mr. Nesterenko said. He added that Russia expected “it will be possible to find a common denominator.”

In Senate testimony on Tuesday, Mr. Gates said that Russia might “partner with us and Poland and the Czech Republic in going forward with missile defense.” American policymakers have long sought common ground with Russia on missile defense, but Mr. Gates’s remarks were unusually specific, suggesting that one option might be a jointly operated facility on Russian territory.

The remarks passed without notice in the United States but were picked up by major Russian newspapers like the daily Kommersant, which described the “sensational statement” in a front-page article in Thursday’s edition.

Moscow has long protested American plans to build a radar site in the Czech Republic and to deploy 10 interceptor missiles in Poland, arguing that the system could target Russia. Two years ago, Vladimir V. Putin, then the president, proposed jointly operating a radar station in Azerbaijan, a former Soviet republic, or one on Russian territory, but American military officials did not see them as substitutes for the planned Czech site.

The Obama administration appears to be reconsidering the idea of collaborating on missile defense as part of the “reset” of its relations with Russia.

During testimony before the Senate on Tuesday, Mr. Gates said he believed that Russian leaders now agreed with Washington on the potential nuclear threat posed by Iran.

“When I first met with President Putin and talked about this, he basically dismissed the idea that the Iranians would have a missile” capable of reaching Europe, Mr. Gates said. “And the fact of the matter is, the Russians have come back to us and acknowledged that we were right in terms of the nearness of the Iranian missile threat.”

He said Washington had put forward some options for collaboration, among them “putting radars in Russia, having data-exchange centers in Russia.” He said at the July summit meeting between Mr. Obama and the Russian president, Dmitri A. Medvedev, that the leaders could “make some steps where they will partner with us and Poland and the Czech Republic in going forward with missile defense in this third site.”

A spokesman for Mr. Gates had no comment on Thursday.

Moscow received the remarks coolly, with Mr. Nesterenko commenting that they “reflect the U.S.’s wishful thinking, rather than the way things actually are.”

For Russia, any reconfiguration that preserves sites in Poland and the Czech Republic “is just window dressing,” said Dmitri V. Trenin, a political analyst.

“I’m not sure everyone in the U.S. understands how much is at stake as far as the Russians are concerned,” said Mr. Trenin, director of the Carnegie Moscow Center. “The issue for the Russians is, what are the U.S.’s long-term intentions vis-à-vis Russia? And they are looking at missile defense for the answer to that question.”

An unwillingness to scrap the Eastern European facilities would be seen by hawks in Moscow as evidence that “the hidden agenda is to contain and destroy Russia,” he said.

Some observers saw positive signs in the exchange, noting that missile defense might ultimately matter more to Russia than renegotiating the Strategic Arms Reduction Treaty, the mutually agreed-upon first step in the “reset.” Maj. Gen. Vladimir Dvorkin, a researcher at the Russian Academy of Sciences, said a radar site in Russia was only one in an array of options for reconfiguring missile defense. Others, he said, are the use of Russian radars in Belarus, Russian missile-testing ranges, Russian expertise in antimissile rockets or even Russian S-400 missile complexes as part of the shield.

“What’s new,” he said, “is a desire and determination for cooperation on many issues.”

Michael Schwirtz contributed reporting from Moscow.

New York Times