NATO and Russia have failed to reach an agreement to cooperate on the alliance's plan for a missile defense system in Europe.

At a meeting Wednesday in Brussels, NATO rejected Moscow's proposal, which would divide the continent into Russian and NATO zones of responsibility.

But NATO Secretary-General Anders Fogh Rasmussen said the two sides could reach an agreement in time for the next summit in May 2012. He expressed hope that Russia and NATO could develop two missile defense systems that would exchange information.

Russia's Defense Minister Anatoly Serdyukov said NATO's position is not acceptable, but that Russia is ready to continue with the dialogue.

Russian leaders have fiercely opposed the idea of a U.S.-built missile shield in Europe, saying it would undermine its defense capabilities. But President Dmitry Medvedev agreed at a NATO summit in Lisbon in November to explore the possibility of cooperating on the system. Since then, Moscow has demanded legally binding assurances that the missile shield is not aimed at Russia, which the alliance refuses to give.

The United States has repeatedly said the planned defense system is not aimed against Russia, but is designed to counter the threat from rogue nations such as Iran.

At the summit in Brussels Wednesday, NATO ministers also approved a set of reforms aimed at simplifying the structure of the alliance while keeping its strength. Under the plan, some bases are to be closed and some others to be relocated.