The United States is working on unspecified economic sanctions against Russia, but there's not much support from the allies.
The threat of economic sanctions has not kept Russia from taking a tighter hold on Ukraine's Crimean Peninsula.
Will Sparks is an analyst with the Eurasia Group, a leading political risk consultancy. Does he think the U.S. and Europeans are willing to let Putin keep Crimea?
"I don't think they much of a choice," Sparks said.
"The Europeans don't want a direct confrontation with the Russians because Europe draws 28 percent of its natural gas from Russia," he said.
Two-thirds of that gas travels in pipelines through Ukraine.
Germany gets 36 percent of its gas from Russia, Italy 27 percent, France 23 percent. The U.S. has little economic leverage; only 2 percent of its trade is with Russia.