The Pentagon says there is no indication that Russian troops massed near the border with Ukraine are conducting routine military exercises, and that the buildup is doing nothing to de-escalate tensions in the region.
Press secretary Rear Admiral John Kirby said Thursday that "thousands" of Russian troops have been deployed along the border with Ukraine.
"They continue to reinforce, and it continues to be unclear what exactly the intent there is...We've seen no specific indications that exercises are taking place."
Russian Defense Minister Sergei Shoigu told U.S. Defense Secretary Chuck Hagel by telephone last week that the troops were conducting "springtime exercises" and assured him the troops would not cross the border.
Kirby said that the presence of these troops along Ukraine's border contributes to heightened tensions and instability.
"It does nothing to de-escalate the tension in Ukraine. It does nothing to improve stability in that part of the world."
Several media outlets reported Wednesday that Western intelligence agencies believe Russia now has more than 30,000 troops on its border with eastern Ukraine, and quoted unnamed officials as saying further Russian military incursions into Ukraine are possible.
CNN quoted an unnamed Obama administration official as saying, "The likelihood of a further Russian incursion is more probable than it was previously thought to be."
Secretary Hagel said Wednesday that Russia has continued to build up military forces along its border with Ukraine, despite assurances it has no intention to invade.
On Sunday, NATO's Supreme Allied Commander Europe, U.S. Air Force General Philip Breedlove, said Russia had built up a large force on Ukraine's eastern border that could move westward into Moldova's mainly Russian-speaking separatist Transdniestria region.
Breedlove said the Russian force deployed on the Ukrainian border was "very, very sizeable and very, very ready."
Intelligence sources in Ukraine tell a VOA reporter that Russian forces have established a field hospital in Russia's Bryansk region about 20 kilometers from the border with Ukraine.
Eight Republican members of the U.S. House of Representatives' Armed Services Committee sent a letter to the White House on Wednesday saying there is "deep apprehension that Moscow may invade eastern and southern Ukraine, pressing west to Transdniestria, and also seek land grabs in the Baltics."
The three Baltic states - Latvia, Lithuania and Estonia - are NATO members.