Two Russian navy ships will join NATO's (search) anti-terrorist patrols in the Mediterranean later this week, but that doesn't make the defensive alliance an ally, Russia's defense minister said on Tuesday.

Sergei Ivanov said the two ships from Russia's Black Sea Fleet (search) would be taking part in NATO's Operation Active Endeavor (search) until early next year.

Operation Active Endeavor has monitored shipping in the eastern Mediterranean and Straits of Gibraltar since the Sept. 11, 2001, attacks on the United States. In March, the alliance extended the operation to the whole of the Mediterranean. Russia pledged earlier this year to contribute its ships to the effort.

Allied officials claim the mission has deterred terrorists from carrying out attacks on shipping or using Mediterranean sea routes to transport material. About two dozen NATO ships are taking part in the operation.

Russia signed a partnership agreement with NATO in 2002, outlining cooperation in counterterrorism, nonproliferation, peacekeeping and other fields.

Moscow's relations with the United States and NATO have improved due in part to President Vladimir Putin's support for Washington after the Sept. 11 attacks, but Russia has continued to voice concern about the alliance's eastward expansion.

"Any NATO country is of course neither an ally nor an enemy to us," Ivanov told the daily Komsomolskaya Pravda.