Russian President Dmitry Medvedev says a planned U.S. missile defense system in eastern Europe is aimed at Russia.
Mr. Medvedev's remark comes one day after U.S. and Polish negotiators reached a preliminary agreement to deploy part of the system in Poland.
Earlier, Russian officials said the timing of the agreement - reached during the crisis with Georgia - proves the missile shield is not related to a threat from Iran, as the United States has claimed.
U.S. Secretary of State Condoleezza Rice, speaking in Tbilisi Friday, said U.S. officials have made extensive efforts to assure Russia the missiles are only for defensive purposes.
The United States and Poland have been discussing the missile defense plan for the past 18 months.
A top Russian general, General Anatoly Nogovitsyn, also said Poland's agreement to host the missile defense system exposes the country to the threat of attack.
Polish Prime Minister Donald Tusk has said a number of details remain to be resolved before the two countries sign a final agreement.
Mr. Tusk said the United States had agreed to Polish demands for greater military cooperation.
U.S. President George Bush's spokeswoman, Dana Perino, says the White House welcomes Thursday's preliminary agreement, saying missile defense is a huge contribution to NATO's collective security.
The United States wants to base 10 interceptor missiles in Poland and a radar system in the Czech Republic as part of a system to counter missile attacks from hostile states. Prague has already agreed to the deal.
Some information for this report was provided by AFP and Reuters.