"We completely reject a referendum patched together in a few weeks with Russian military personnel basically taking over Crimea. We reject its legitimacy. It is contrary to international law. It is contrary to the Ukrainian constitution," Obama told reporters following his meeting with Ukrainian Prime Minister Arseniy Yatsenyuk.
"I know that we've heard from the Russian Federation this notion that these kinds of decisions are often made in other places, and they've even analogised it to Scotland or other situations of that sort," he said.
"The issue now is whether or not Russia is able to militarily dominate a region of somebody else's country, engineer a slapdash referendum, and ignore not only the Ukrainian constitution but a Ukrainian government that includes parties that are historically in opposition with each other - including the party of the previous president," he said.