The United States has refused to participate with Russia in NATO's Operation Active Endeavour naval antiterrorism exercise, a source in the Russian Black Sea Fleet said Friday.

Washington initiated the Active Endeavour exercises along with other NATO members after the terrorist attacks on the United States on September 11, 2001, with Russia joining the exercise in 2005 by offering ships from its Black Sea Fleet.

"The Ladny guided missile frigate of the Black Sea Fleet, which participated in the exercise, is returning to Sevastopol naval base," the source said.

Russia's NATO envoy Dmitry Rogozin announced Thursday that the Russian Defense Ministry was temporarily suspending military cooperation with NATO until a political decision on relations had been made.

NATO foreign ministers said after talks Tuesday that the alliance was freezing contacts with Russia until it pulled its troops out of Georgia, but stopped short of stronger measures.