(CNN) -- U.S. President Barack Obama greeted a reported ceasefire between Ukraine and Russia with skepticism Wednesday, saying it was too early to see if all sides would follow through. Any ceasefire effort has not worked up to now, he said, "either because Russia has not supported it or pretended it is not controlling the separatists" in eastern Ukraine. "Having said that, if in fact Russia is prepared to stop financing, arming, training and in many cases joining with Russian troops activities in Ukraine, and is serious about a political settlement, that is something that we all hope for," Obama added.