Lithuania signed up for NATO's partnership plan Thursday, becoming the first former Soviet republic to embrace a deal that offers cooperation to former foes while denying them full membership.

Before signing the document at NATO headquarters, President Algirdas Brazauskas told ambassadors of the 16 NATO nations that Lithuania eventually plans to join the North Atlantic Treaty Organization.That aim could upset Russia, Lithuania's neighbor and former ruler.

Moscow opposes any eastward expansion of the Western military alliance and reacted with alarm this month when Lithuania became the first of its former Warsaw Pact satellites to formally apply for NATO membership.

President Boris Yeltsin's spokesman, Vyacheslav Kostikov, warned then that Lithuania's move could provoke "a negative reaction in Russian public opinion" and play into the hands of the country's extreme nationalists.

Lithuania became the second former Warsaw Pact state to accept the limited NATO offer. Romania signed up Wednesday. Poland and Estonia are expected to do likewise next week, followed by other east European nations.

The program, proposed by the United States, allows east European nations to join NATO in military exercises, peacekeeping operations and other activities. But it does not grant them membership or security guarantees, particularly that an attack against one member is considered an attack against all.

The program was designed to balance Russia's worries about the enlargement of NATO with the desires of the new democracies in central and eastern Europe for closer ties.

Brazauskas sought to allay Russian fears.

"Lithuania's position regarding NATO membership is not directed against any neighboring or other European states," he said in the speech at NATO headquarters.

The integration of eastern European nations into NATO and other Western structures would "significantly support the strengthening and continuity of democratic processes in Russia," he said.