U.S. Warns Russia a Ukraine Intervention Would Be a ‘Grave Mistake’

President Barack Obama warned Russia not to intervene in the Ukraine, as United States leaders at the White House, Pentagon and State Department closely monitor reports from Crimea that, according to Agence France Press , as many as 2,000 Russian-backed troops have entered the eastern region.

"There will be costs for any military intervention in Ukraine," Obama said at a White House briefing late Friday.

Earlier, White House spokesman Jay Carney warned Russia: “Intervention would be a grave mistake.”

“We are watching to see … whether or not Russia is doing anything that might be crossing the line in any way,” Carney said. When asked what “crossing the line” means, he didn’t elaborate.

Secretary of State John Kerry spoke with Russian Foreign Minister Sergey Lavrov on Friday afternoon. Meanwhile, Defense Secretary Chuck Hagel said the Pentagon is “closely monitoring it and we are continuing to talk with our Russian counterparts about what their intentions are; what the motives are behind some of this.”

Carney said White House officials are “concerned” about reports of the troop movements and were “seeking clarification” from Russia, through Kerry. “So I'm not going to speculate or frame it beyond the reports we've seen and the concern that we're expressing.”

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Russian officials are giving the U.S. conflicting information that conflicts what’s been unfolding on the ground in Ukraine. Russian officials have reassured the Obama administration that they will not intervene. The Daily Beast reported that Russian-backed troops in Crimea are Russia’s version of Blackwater, the U.S. military contractor that became controversial during the Iraq war. CNN reported military vehicles rolling in with their insignias blacked out. These troops have reportedly blocked roads and airport. Ukraine officials describe it as a “military invasion.”

(Click Below to Explore the Crimean Peninsula)

Carney said it’s been difficult to verify fast-moving developments on the ground. “Other reports about things and developments in Ukraine are matters that we're looking into, that we're seeking clarification on, we're discussing with Ukrainian leaders as well as Russian leaders and others. I can't go through with you each report and what the, you know, bottom-line truth behind each report is,” he said.

“What I can tell you is that we're concerned about reports of suggestions that there might be intervention by an outside state, and we have conveyed that. And we would point to assurances by the Russian government that they respect the territorial integrity of Ukraine,” he said.

Hagel urged calm so that no nation’s actions could be misinterpreted. At Thursday’s NATO meeting in Brussels, Hagel said, “Until we know more details of what's really happened there, who's in charge, I think the focus should be on … let's keep the tensions down, let's see no provocative actions by anyone, any military.”

“These are difficult times. We all understand that,” he said. “But this is a time for very cool, wise leadership on the Russian side, on everybody's side here.”