President Obama, as he has done in virtually every foreign policy conflict since he entered office, is trying to build a broad coalition of world leaders to repeat and amplify his  message, this time with the goal of pushing Russia to withdraw forces from the Crimea region in the Ukraine.

White House officials say the president spent much of Sunday in calls with the leaders of the United Kingdom, Poland and Germany. In describing the calls, the administration said “the leaders affirmed the importance of unity within the international community in support of international law.”

“There’s a unified view by all of the foreign ministers I talked with yesterday, all of the G8 and more, that they’re simply going to isolate Russia,” Secretary of State John Kerry said in an interview on NBC’s Meet the Press on Sunday, laying out the administration’s strategy.

What’s not clear if Obama’s coalition-building approach will be effective, as it has been in getting Iran to agree to negotiations over its nuclear weapons program or largely ineffectual, as thousands have died in a bloody civil war in Syria that the U.S. and its partners have tried to stop.

With Russia, Obama faces  some unique challenges. Russian President Vladimir Putin may be more interested in expanding the reach and power of his government and Russia overall than appealing to the American president or winning more popularity globally.

The effect of broad economic sanctions was devastating to Iran, but may be less so to a bigger economy like Russia. And any use of the U.S. military, which Obama briefly deployed in Libya, is  verboten in a conflict with a country with a large army like Russia.