Seeking to isolate Russia, President Barack Obama and Western and Asian allies have moved to indefinitely cut Moscow out of a major international coalition, including cancelling an economic summit President Vladimir Putin planned to host this year.
The moves today came amid a flurry of diplomatic jockeying at The Hague, Netherlands, as the US and Europe grappled for ways to punish Russia for its annexation of the Crimean Peninsula and to prevent Moscow from pressing further into Ukraine. The world powers warned that they were prepared to "intensify actions" against Russia, including ordering more severe economic sanctions, if the Kremlin escalates its incursion into Ukraine.
Separately in the Hague, in an unexpected development, Russia's foreign minister met with his Ukrainian counterpart, the highest level of contact between the two nations since Russia moved forces into Crimea nearly a month ago.
Obama huddled with the leaders of Britain, France, Germany, Italy, Canada and Japan for an emergency meeting of the Group of Seven. In a joint statement after the evening meeting, the leaders said they were suspending their participation with Russia in the Group of Eight major industrial nations until Moscow "changes course."
The G7 leaders instead plan to meet this summer in Brussels, symbolically putting the meeting in the headquarters city of the European Union and Nato, two organisations seeking to bolster ties with Ukraine.
"Today, we reaffirm that Russia's actions will have significant consequences," the leaders' statement said. "This clear violation of international law is a serious challenge to the rule of law around the world and should be a concern for all nations."
Russia's actions have sparked one of Europe's deepest political crises in decades and drawn comparisons to the Cold War era's tensions between East and West.
Obama and other Western leaders have condemned Russia's movements as a violation of international law and have ordered economic sanctions on Putin's close associates, though those punishments appear to have done little to change the Russian leaders' calculus.
Hours before world leaders began meeting in The Hague, Russian forces stormed a Ukrainian military base in Crimea, the third such action in as many days. Ukraine's fledgling government responded by ordering its troops to pull back from the strategically important peninsula.
In the US, meanwhile, the Senate moved toward a vote on Russia sanctions and Ukraine aid while Ukraine pushed for the United Nations General Assembly to adopt a resolution reaffirming the country's territorial integrity and declaring that the referendum in Crimea that led to its annexation by Russia "has no validity."
In the Hague, the G7 leaders also discussed plans for increasing financial assistance to Ukraine's central government.
Obama was expected to be seeking support from European leaders for deeper sanctions on key sectors of the Russian economy, including its energy industry.