NATO chief sees ‘high probability’ of Russian intervention in Ukraine

The chances that Russia could take military action in eastern Ukraine are rising, the head of NATO said on Monday.

“There is a high probability” Russian forces massed along Ukraine’s border could soon intervene, NATO chief Anders Fogh Rasmussen told Reuters.

He also said that he saw no indications that Moscow was withdrawing any of the estimated 20,000 troops along the border.

"We see the Russians developing the narrative and the pretext for such an operation under the guise of a humanitarian operation, and we see a military buildup that could be used to conduct such illegal military operations in Ukraine," Rasmussen said.

On Saturday the Obama administration warned Russia that any military action taken inside Ukraine, even under the auspices of humanitarian aid, would be seen as a violation of international norms.

President Obama had calls with British Prime Minister David Cameron and German Chancellor Andrea Merkel during which the trio agreed that any Russian intervention without Ukraine’s consent would “provoke additional consequences,” the White House said.

In the spring, the Kremlin deployed roughly 40,000 troops to the border, drawing that number down to 1,000 in June.

However, after being hit by new sanctions over its continued support for rebels in eastern Ukraine, Moscow has ramped troop levels back up to around 20,000 and dispatched them closer to the border, moves that have been condemned by Western leaders.

On Monday Sen. Bill NelsonClarence (Bill) William NelsonOvernight Tech: Senate panel subpoenaed ex-Yahoo chief | Twitter gives all users 280 characters | FBI can't access Texas shooter's phone | EU wants tax answers from Apple Overnight Cybersecurity: What we learned from Carter Page's House Intel testimony | House to mark up foreign intel reform law | FBI can't access Texas shooter's phone | Sessions to testify at hearing amid Russia scrutiny Former Yahoo CEO subpoenaed to appear before Congress MORE (D-Fla.) announced he would travel to the region for a "series of meetings on defense planning and other issues."

Russian President Vladimir Putin's "offer of humanitarian aid is a guise to invade," he said in a statement.

Nelson last month became one of the first Democratic lawmakers to split with Obama over providing lethal equipment to Ukraine's military.

“I think it's going to boil down over the course of the next six months that we need to supply them with the weapons so that they can protect themselves,” Nelson said after a classified briefing on the security situation in Ukraine.

He is slated to leave for the region later this week, though officials times will not be released, according to the press release.

--This report was updated at 11:14 a.m.