Moscow: Russia has serious concerns about US plans to deploy missile interceptors in Romania, the Foreign Ministry said on Friday.

The statement from ministry spokesman Andrei Nesterenko reflected Moscow's irritation about the US missile defense plans and signaled tensions in relations with Washington.

Nesterenko said that Russia has been annoyed to learn about the move from the media.

"We are worried that we find out about important decisions regarding the US missile defense in Europe from the media rather than our official counterparts in Washington or Bucharest," Nesterenko told a briefing.

Nesterenko wouldn't comment on whether the dispute could affect talks with the United States on a key nuclear arms reduction treaty that expired in December.

But other Russian officials, including the nation's top military officer, recently said the US missile defense plans threaten Russia and have slowed down negotiations on a successor deal to the 1991 Strategic Arms Reduction Treaty.

Russia and the US had hoped to reach agreement before START expired on Dec. 5, but differences persisted. Still, Sergei Prikhodko, President Dmitry Medvedev's foreign policy adviser, said Friday that the Kremlin believes the treaty could be signed in March or April, Russian news agencies reported.

Nesterenko also voiced skepticism about Washington's explanation that the interceptors were needed to protect US troops and NATO allies against the Iranian missile threat.

"Russia has serious questions regarding the true purpose of the US missile defense in Romania," Nesterenko said. "That is why we will consistently oppose any dubious unilateral actions in the missile defense field that could have a negative impact on the international security."

He added that the US plans would make a "fragile European security structure hostage to the imaginary missile threats that are defined unilaterally."

Russia has applauded President Barack Obama's decision to scrap Bush administration plans for missile defense systems in Poland and the Czech Republic. But Moscow has grown increasingly critical of the planned site in Romania and also criticized the US plans to deploy Patriot air defense missiles in Poland.

General Nikolai Makarov, the chief of general staff of the Russian armed forces, said that a revised US plan to place missiles in Europe undermines Russia's national defense, rejecting Obama administration promises that the plan is not directed at his country.

On Tuesday, John Beyrle, the US ambassador to Moscow, tried to reassure Russia that the placement of American missile interceptors in Romania would not threaten Russia's nuclear capability and is designed only to intercept medium-range missiles, which Russia doesn't have.