NATO ministers, meeting in Brussels, are discussing the possibility extending a missile defense system the United States wants to deploy in central Europe.
Thursday's meeting marks the first time the alliance has formally discussed the missile shield, which is opposed by Russia.
Western diplomats said ministers are preparing for a decision next year on whether NATO develops its own short-range missile defenses to augment the U.S. shield.
Under the U.S. plan, missile interceptors would be deployed in Poland, and radar in the Czech Republic. However, four NATO countries - Bulgaria, Romania, Greece and Turkey - are only partly covered or left out of the U.S. plan.
Last week, Russian President Vladimir Putin said Russia could drop its opposition to the plan, if the weapons system is broadened to include a Soviet-built radar base in Azerbaijan.
NATO ministers also expected to discuss the proposal with Russia's new Defense Minister Anatoly Serdyukov.
Mr. Putin had earlier threatened to point Russian missiles at Wstern Europe, if the alliance adopts the U.S. plan.
Moscow has argued the U.S.-built missile defense system would destabilize eastern Europe and lead to a new arms race. Washington insists Russia has nothing to fear from the system, which authorities say is aimed at defending against attacks from states such as Iran and North Korea.
Some information for this report was provided by AFP, AP and Reuters.