President Obama said Friday that the U.S. government is “deeply concerned” by reports of Russian “military movements” inside Ukraine, warning that any violation of Ukraine’s sovereignty would be “deeply destabilizing.”

“There will be costs for any military intervention in Ukraine,” he said, without specifying what those costs might be.

But a senior U.S. official told Fox News the Pentagon has not prepared “any military contingencies” for Ukraine.

Obama spoke Friday amid reports that suspected Russian soldiers had landed at a military base in the Crimean peninsula. Officials told Fox News they see “evidence of air and maritime movement into and out of Crimea by Russian forces.”

Later Friday, Mike Rogers, chairman of the House Select Committee on Intelligence, issued a statement saying, “It appears that the Russian military now controls the Crimean peninsula.  This aggression is a threat not only to Ukraine, but to regional peace and stability.  Russia’s latest action is yet another indicator that Vladimir Putin’s hegemonic ambitions threaten U.S. interests and allies around the world.”

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