Pentagon says it is monitoring 'unusual' Russian troop movements near Ukraine

"Any escalatory or aggressive actions by Russia would be of great concern," spokesman John Kirby told reporters.

The United States is watching "unusual" Russian troop movements near the border with Ukraine, the Pentagon said.

“We continue to monitor this closely,” Pentagon press secretary John Kirby said in a Friday briefing, amid reports that Moscow had placed some 90,000 troops near the border with Ukraine.

“Without getting into greater detail right now, I think it's really a matter of scale," Kirby said at the Pentagon. "It's a matter of the size of the units that we're seeing."

Additionally, he said: "Any escalatory or aggressive actions by Russia would be of great concern."

Moscow has downplayed concerns about the troop placements.

“Russia maintains troops presence on its territory wherever it deems necessary,” Kremlin spokesman Dmitry Peskov said Wednesday on a press call.

The Russian navy earlier this week practiced destroying mock-enemy forces in the Black Sea, while two U.S. Navy warships traversed waters in the region.