Russia called for an emergency meeting of the United Nations Security Council on Tuesday over what it called an urgent humanitarian situation in Ukraine, according to a report from the Russian news agency ITAR-TASS.

"We are convening an emergency meeting of the United Nations Security Council on the humanitarian situation in Ukraine," Russian Ambassador to the U.N. Vitaly Churkin was quoted as saying.

Earlier on Tuesday, the Russian Foreign Ministry said the U.N. and the International Committee of the Red Cross expressed "readiness" to discuss its plan to deploy a "humanitarian mission" to Ukraine, which some consider to be a pretext for an invasion by Russian forces.

Russia has significantly built up its troop presence along the Ukrainian border in recent weeks, according to U.S. officials, making it ready for a potential large-scale invasion of southeastern Ukraine if Russian President Vladimir Putin so chooses.



According to a report in The New York Times, Russia has nearly doubled its troop presence along the border, adding 17 battalions and 19,000 to 21,000 troops who now compose a "battle-ready force of infantry, armor, artillery, and air defense within a few miles of the border."



The White House has openly worried about what would be, for all intents and purposes, an invasion under the guise of a "peacekeeping" operation.

"We’ve seen a significant re-buildup of Russian forces along the border, potentially positioning Russia for a so-called humanitarian or peacekeeping intervention in Ukraine," deputy national security adviser Tony Blinken said last week.

"That’s a very real option," a senior Defense Department official told The Times. "And should Putin decide, he could do that with little or no notice. We just don’t know what he’s thinking."

Of the new developments, a White House official told Business Insider it is "concerned" about Russia's statements indicating it may send "peacekeepers" into Ukraine.

"Russia has a track record of abusing the term 'peacekeeping' as a cover for unlawful military intervention and occupation," the official said. "Given its unlawful attempted annexation of Crimea, which we do not recognize, it is deeply troubling to hear any discussion of Russian 'peacekeepers' in Ukrainian territory. Such statements are destabilizing and unhelpful."

Ukraine on Tuesday called on Russia to halt its buildup of forces along the border, which have come in the wake of major gains by Ukrainian forces against pro-Russian separatists. The escalation in fighting over the past few weeks has sent thousands of Ukrainian residents fleeing their homes. The U.N.'s refugee agency said on Tuesday that 117,000 people had been displaced inside Ukraine by the conflict.

Stocks tumbled on the flurry of reports of the Russian buildup along the border. The Dow was down as much as 150 in late-day trading.

This post has been updated.