THE HAGUE, Netherlands -- The United States and its closest allies on Monday cast Russia out of the Group of Eight industrialized democracies, their most exclusive club, to punish President Vladimir Putin for his lightning annexation of Crimea, while threatening tougher sanctions if he escalates aggression against Ukraine.
President Barack Obama and the leaders of Canada, Japan and Europe's four strongest economies gathered for the first time since the Ukraine crisis erupted last month, using a closed two-hour meeting on the sidelines of a summit about nuclear security to project a united front against Moscow.
At the opening of that two-day summit, Japan pledged to return to the United States more than 700 pounds of weapons-grade plutonium and a supply of highly enriched uranium. The Nuclear Security Summit is the third in a series of meetings established after a landmark 2009 speech by President Barack Obama in which he said non-secure nuclear material presents "the most immediate and extreme threat to global security."
In bouncing Russia from the G-8, the world leaders stopped short, at least for now, of imposing sanctions against what a senior Obama administration official called vital sectors of the Russian economy: energy, banking and finance, engineering and the arms industry. Only further aggression by Mr. Putin -- like rolling his forces into the Ukrainian mainland -- would prompt that much-harsher punishment, the countries indicated in their joint statement, called The Hague Declaration.
Some critics of the administration said the suspension of Russia from the G-8, which administration officials acknowledged was largely symbolic, showed a lack of resolve among the allies to take tougher steps to undo Mr. Putin's annexation of Crimea. But it signified a firming of Western resolve compared to the early days of the Crimea crisis, when Germany and some other allies said it was premature to consider excluding Russia from the club of industrial democracies. Having Russia as part of that group since 1998 was meant to signal cooperation between East and West, and its exclusion inevitably raises new echoes of Cold War-style rivalry.
Announcing that they would boycott a G-8 meeting planned for Sochi -- Mr. Putin's Black Sea showcase for the recent Winter Olympics -- the seven countries who met in The Hague said they instead would gather by themselves in June in Brussels, headquarters of NATO and the European Union.
"We will suspend our participation in the G-8 until Russia changes course," the seven countries declared in what constituted a subtle appeal to Russian leaders outside Mr. Putin's circle to press for a switch in direction.
After the Soviet Union collapsed in 1991, Russia eagerly sought to join the tight circle of the top economies, eventually gaining entry in 1998. For all that, Mr. Putin shrugged off the threat of canceling the Sochi summit this month -- a shoulder shrug imitated in The Hague by his foreign minister, Sergei Lavrov, on Monday -- it is a blow to the Kremlin's search for prestige.
Mr. Putin took membership in the group so seriously that he went all out when it came time for Russia to host the annual meeting for the first time. He rebuilt a broken-down czarist-era palace outside his hometown, St. Petersburg, in part with the summit in mind, adding a series of new mansions to the grounds for each leader to stay in. The Kremlin hired a Western public relations agency to tout its status as host.
"Obviously, it's mostly symbolic, but symbols do matter," said Michael McFaul, the just-departed U.S. ambassador to Moscow. "The G-8 was something they wanted to be part of. This for them was a symbol of being part of the big-boy club, the great power club -- and the club of democracies, I might add."
The Obama administration voiced satisfaction that the West was united in punishing Russia, both now and in future, if it does not reverse course. "There really wasn't much disagreement" at the meeting either about Russia or the need to swiftly aid Ukraine, the senior administration official said.
Also on the sideline of the nuclear security summit Monday, Mr. Lavrov, the Russian foreign minister, met with his Ukrainian counterpart for the first time and demanded more autonomy for Ukraine's regions, even as Ukraine, under pressure, ordered its troops out from Crimea after the Russian seizure of military bases there.
Mr. Lavrov, in an unexpected move, agreed to the highest level meeting yet between the Russian government and a representative of the new Ukrainian government that Moscow has opposed vociferously over the past month. He told Ukrainian Foreign Minister Andriy Deshchytsia that Russia continues to want constitutional changes in Ukraine that would give more autonomy to all regions of Ukraine. Before the meeting, Mr. Deshchytsia said his government fears a Russian military buildup near Ukraine's border.
The concerns have been deepened in by the intense military pressure Russia has applied in Crimea since Mr. Putin formally annexed the peninsula last week. Russian forces have commandeered ships and broken into walled military installations with armored personnel carriers.
In the bay of Donuzlav in western Crimea, dozens of Ukrainian sailors marooned on the Konstantin Olshanskiy navy landing vessel abandoned ship Monday after weeks of tension and uncertainty. The Olshanskiy and two other warships have been trapped in the bay since Russian forces scuttled mothballed ships at the bay's inlet. The sailors, using a small rubber boat that needed several trips to ferry them to land, were greeted by hecklers on the shore.
Associated Press contributed.