MOSCOW - Russia's foreign minister urged the United States on Saturday to freeze plans for missile defense installations in eastern Europe during negotiations and warned that the proposal -- intended to serve as a buffer against Iran -- could backfire.

Russian Foreign Minister Sergei Lavrov's comments, reported by Russian news agencies, suggested the Kremlin is unhappy that the United States has continued discussions on its plans to deploy facilities in Poland and the Czech Republic following Russia's counteroffer of joint use of a radar station in Azerbaijan.

"It's necessary for Washington, at a minimum, to freeze the deployment of missile defense elements in Europe for a period of study and negotiations on the Russian proposal," ITAR-Tass quoted Lavrov as saying.

Lavrov also warned that the U.S. missile defense plans could hamper efforts to ease international concerns about Iran's nuclear program, RIA-Novosti reported. The United States has said the missile defense shield is intended to protect against a potential Iranian threat.

Lavrov said there was no proof that Iran was seeking to develop nuclear weapons, but that the missile shield could further provoke the Iranian government, which is already facing international sanctions for its disputed atomic program.

The U.S. system calls for a radar screen in the Czech Republic to watch for missile threats, and 10 interceptor rockets in Poland to shoot down any missiles. Both Bush and Polish President Lech Kaczynski said Friday the system would not threaten Russia. The Kremlin argues that the system would undermine its nuclear deterrent.

President Vladimir Putin, who has led Russia's bitter objection to U.S. plans to deploy a missile-defense radar in the Czech Republic and interceptors in Poland, surprised President Bush with the offer of joint use of the radar station in Azerbaijan, which borders Iran.

Meeting with Putin on Thursday during a Group of Eight summit in Germany, Bush agreed to consider the proposal. But the Bush administration made clear it was not abandoning plans for a program in Poland and the Czech Republic -- Cold War-era Soviet satellites that are now in NATO.

Putin added clarity to his offer Friday by suggestion locations for missile interceptors if Azerbaijan were to be used for the radar element, saying they could be placed in Turkey or Iraq, or on sea platforms.

Secretary of State Condoleezza Rice told The Associated Press on Friday that "one does not choose sites for missile defense out of the blue" and that it was not yet clear "whether Azerbaijan makes any sense in the context of missile defense."