BUCHAREST, Romania — President Putin of Russia scored a major diplomatic coup by scuttling the North Atlantic Treaty Organization membership bids of Ukraine and Georgia even before he reached the NATO summit.

NATO’s plan to expand further into former Soviet turf collapsed yesterday when leaders — anxious to avoid angering Moscow — opted not to put the strategically important nations on track for membership.

Mr. Putin had strongly warned the military alliance against moving to bring Ukraine and Georgia aboard. He even threatened that Russia could point its nuclear missiles at Ukraine if it joins NATO and hosts part of an American missile defense system.

In the waning days of his eight years as president, Mr. Putin demonstrated his strength — successfully driving a wedge through the NATO alliance.

America, Canada, and Central and Eastern European nations backed the membership bids of Ukraine and Georgia. But Germany, France, and some others resisted it for fear of damaging ties with Russia, a key energy supplier to the continent.

NATO pledged yesterday to embrace Ukraine and Georgia some day, but the failure to grant them a specific route to membership was a major foreign policy success for Mr. Putin just over a month before he steps down as president.

Russia has been unable to prevent Western recognition of Kosovo independence or to block American missile defense plans. The collapse of NATO’s expansion plan marks the first time since the Soviet collapse when Russia got the upper hand in a dispute with the West.

“Clearly Putin is victorious,” a Russian political analyst with close ties to the Kremlin, Sergei Karaganov, said. “He has changed the tone of relations between Russia and the West.”

Mr. Putin’s coup comes after the Kremlin closed a series of pipeline deals, dashing Western hopes of easing the European Union’s dependence on Russian energy.