NATO's top military commander said Sunday that Russia had a large force on Ukraine's eastern border and said he was worried it could pose a threat to Moldova's mainly Russian-speaking separatist Transdniestria region.
NATO's supreme allied commander Europe, U.S. Air Force Gen. Philip Breedlove, voiced concern about Moscow using a tactic of snap military exercises to prepare its forces for possible rapid incursions into a neighboring state, as it had done in the case of Ukraine's Crimea.
Russia launched a new military exercise, involving 8,500 artillery men, near Ukraine's border 10 days ago.
"The [Russian] force that is at the Ukrainian border now to the east is very, very sizeable and very, very ready," Breedlove told an event held by the German Marshall Fund think tank.
White House aid and deputy national security adviser Tony Blinken echoed Breedlove's concerns in an interview with CNN Sunday. He said it's possible that Russia could invade eastern Ukraine, and that even U.S. military assistance would be unlikely to prevent it.
The U.S. is looking at providing military support to Ukraine, Blinken said, but, "it's very unlikely to change Russia's calculus and prevent an invasion," he added.
The president of ex-Soviet Moldova warned Russia last Tuesday against considering any move to annex Transdniestria, which lies on Ukraine's western border, in the same way that it has taken control of Crimea.
But Russia's deputy defense minister, Anatoly Antonov, said Sunday that Moscow is complying with international agreements limiting the number of troops near its border with Ukraine.
"The Russian Defense Ministry is in compliance with all international agreements limiting the number of troops in the border areas with Ukraine," Antonov was quoted as saying by the state Itar-Tass news agency.
Russian news agency RIA Novosti reported Sunday that the Russian flag was flying over 189 Ukrainian military installations in Crimea after Moscow formally annexed the region from Ukraine earlier this month.
The speaker of Transdniestria's separatist parliament had urged Russia earlier to incorporate his mainly Russian-speaking region.
Transdniestria split from Moldova in 1990, one year before the dissolution of the Soviet Union, amid fears that Moldova would shortly merge with neighboring Romania, whose language and culture it broadly shares.
Breedlove said NATO was very concerned about the threat to Transdniestria, which he said, in Russia's view, was the "next place where Russian-speaking people may need to be incorporated."
"There is absolutely sufficient [Russian] force postured on the eastern border of Ukraine to run to Transdniestria if the decision was made to do that and that is very worrisome."
NATO had tried to make Russia a partner but "now it is very clear that Russia is acting much more like an adversary than a partner," he said.
Breedlove's comments came the day after Russian troops stormed the Ukrainian Belbek air base in Crimea Saturday, armed with guns and stun grenades.
Russian President Vladimir Putin signed a bill Friday formally annexing Crimea to Russia, in a move that provoked expanded U.S. sanctions. Kiev and Washington have said that they do not recognize a Crimean referendum to join the Russian Federation.
According to the head of Crimea's referendum commission, Mikhail Malyshev, 97 percent of voters favored an alliance with Russia in the majority Russian-speaking region.
Al Jazeera and wire services