U.S. Secretary of State Condoleezza Rice and Czech Foreign Minister Karel Schwarzenberg signed the agreement on deploying the radar system, which still needs approval by the Czech parliament, RIA Novosti reported.

"Given this situation, the Russian side will obviously have to take appropriate measures to compensate for the growing potential of threats to its national security. But this is not our choice," the Russian Foreign Ministry said in a statement.

As part of the missile defense system, the United States plans to place interceptor missiles in Poland. A tentative agreement there has been reached.

Earlier, a Russian general said his country wasn't satisfied with U.S. attempts to calm fears over the missile shield bases in Eastern Europe.

Lt. Gen. Yevgeny Buzhinsky, head of Russia's Defense Ministry international cooperation department, told a Russian newspaper U.S. offers to allow Russians some access to the proposed anti-missile installations are vague and come with unacceptable conditions, Novosti said.