US President Barack Obama yesterday vowed Western unity in punishing Moscow for annexing Crimea, ahead of crisis talks that could see Russia excluded from the G8 club of rich nations.
"Europe and America are united in our support of the Ukrainian government and the Ukrainian people, we're united in imposing a cost on Russia for its actions so far," Obama told journalists at Amsterdam's Rijksmuseum.
Obama then headed to The Hague where he has called an emergency Group of Seven summit to discuss what steps to take in the worst East-West standoff since the Cold War.
Russian Foreign Minister Sergei Lavrov is to meet US Secretary of State John Kerry on the sidelines of the Nuclear Security Summit for what may be their most tense talks to date.
It will be their first meeting since Washington imposed financial restrictions on the most powerful members of Putin's inner circle for their decision to resort to force in response to the fall of Ukraine's pro-Kremlin regime after three months of sometimes deadly protests.
Kerry has already warned that Moscow risks losing its coveted place among the G8 because of the Crimea crisis.
British Prime Minister David Cameron said leaders from Canada, France, Germany, Italy, Japan and the United States -- minus current G8 chair Russia -- must discuss the permanent expulsion of Russia from the group, which it was admitted to in 1998 as a reward for choosing a democratic post-Soviet course.
Ukraine's Western-backed leaders have voiced fears of an imminent Russian invasion of the eastern industrial heartland, three weeks after the Kremlin sent troops into the heavily Russified peninsula before sealing its annexation Friday.
Some other former Communist bloc nations fear for their security in the face of Russian expansionism, and Obama reiterated NATO's solemn obligation to mutual defence.
"No one should ever question the commitment of the United States to the security of Europe," he told the Dutch Volkskrant newspaper yesterday, referring to NATO as "the strongest and most effective alliance in human history."