The leaders of the world's top industrialised powers have turned on fellow G8 member Russia, condemning its "clear" violation of Ukraine's sovereignty.
Symbolically billing themselves as the "G7", the leaders said in a statement that Russia's actions were incompatible with the Group of Eight Nations, which Moscow joined in 1997, and said they would not take part in preparatory talks for June's G8 summit in Sochi, Russia.
The statement, signed by the leaders of Britain, Canada, France, Germany, Italy, Japan, the US and the presidents of the European Council and European Commission, was released by the White House.
The leaders said they joined to "condemn the Russian Federation's clear violation of the sovereignty and territorial integrity of Ukraine, in contravention of Russia's obligations under the UN Charter and its 1997 basing agreement with Ukraine".
"We call on Russia to address any ongoing security or human rights concerns that it has with Ukraine through direct negotiations, and/or via international observation or mediation under the auspices of the UN or the Organisation for Security and Cooperation in Europe."
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The statement called on all parties to "behave with the greatest extent of self-restraint and responsibility, and to decrease the tensions."
Russia has been a fully-fledged member of the G8 since it joined in 1997, but the G7 grouping continues to convene when the discussion is limited to economic and financial issues.
The leaders said Russia's actions in sending troops into Crimea contravened the principles on which the G7 and the G8 grouping operates.
"As such, we have decided for the time being to suspend our participation in activities associated with the preparation of the scheduled G8 Summit in Sochi in June, until the environment comes back where the G8 is able to have meaningful discussion.
"We are united in supporting Ukraine's sovereignty and territorial integrity, and its right to choose its own future," the statement said, vowing support for Ukraine's stability and political and economic wellbeing.
The statement also expressed support for the interim government in Kiev's efforts to negotiate a deal with the International Monetary Fund to stave off an economic crisis.
