The United States designated a Chechen militant leader sought by Russia as a terrorist.
The move by Secretary of State Hillary Rodham Clinton on Wednesday on the eve of a visit to Washington by Russian President Dmitry Medvedev would block the assets of Doku Umarov and sanction any individual or company doing business with him.
Umarov has taken responsibility for numerous terrorist attacks including the Moscow subway bombings in March that killed dozens.
The State Department's Coordinator for Counter-terrorism Daniel Benjamin said on Wednesday that the United States would take other unspecified action against Umarov. He said: "We stand in solidarity with the Russian people in our condemnation of these deplorable terrorist acts."