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(CNN) – Western powers slapped sanctions on more than two dozen Russian officials and their allies in Ukraine's Crimea region Monday, while Ukrainian officials vowed they would never accept the territory's annexation by Russia.
In Washington, President Barack Obama warned Moscow: "Further provocations will achieve nothing except to further isolate Russia and diminish its place in the world."
But Democratic Senator Chris Murphy, fresh off a congressional delegation to Ukraine, says today's sanctions do not go far enough.
"(They) make it clear that we're serious about moving forward on sanctions, but they give him room to make a different decision before he officially annexes Crimea," said Murphy, a member of the Senate Foreign Relations Committee.
Putin marched into Crimea because he thought the U.S. "would not take him seriously," and has ambitions beyond the southern Ukranian peninsula, says Murphy.
"He clearly has this vision to reestablish the Soviet Union," said Murphy. "Whether he's going to try and move further to eastern Ukraine, whether he's going to now cut a deal with Kiev, clearly his motivation is to try and bring that whole country back in his orbit."
Currently, says Murphy, the vast majority of Ukraine is moving toward Europe, which would be "a foreign policy disaster for Putin."
"I know this is not his end game," said Murphy.
For more of our interview with Sen. Chris Murphy, check out the video above.