State Department spokeswoman Jen Psaki has said the US is considering a "range of tools" to deal with what it sees as Russian aggression in Ukraine.
She said increased sanctions on Russia are "the most effective tool, the best tool."
"A military solution is not what we think is the appropriate approach so we're taking every tool that we can to see if we can reach a solution here through diplomatic means," she said.
Were the Russians -as Barack Obama claims - weighed down by sanctions, or where the Ukrainians looking to cut their losses?
The new president of the European Council could be "very important" for David Cameron.