U.S. Republican Senator John McCain says a Russian invasion of eastern Ukraine would be a breach of "enormous consequences" and could bring a very sharp response by the United States and Europe.
McCain spoke from Kyiv Saturday as part of a U.S. Senate delegation meeting with Ukraine's interim leaders and the opposition.
The senator said he is deeply concerned about reports of Russian troops moving closer to the eastern Ukrainian border and conducting military exercises.
McCain said if Russia invades Ukraine, the United States and its European allies would contemplate action that they have never thought about before in their relations with Russia.
McCain called Sunday's referendum in Crimea "phony," while Democrat Dick Durbin described it as a "Soviet style" election where the outcome is already known.