Top US national security officials call counterparts as Russia and Ukraine tensions rise | WHAT REALLY HAPPENED X-Frame-Options: DENY X-Frame-Options: SAMEORIGIN

Top US national security officials call counterparts as Russia and Ukraine tensions rise

Top US national security officials have spoken with their Ukrainian counterparts, and America's top general held a call Wednesday with his Russian opposite number amid concern over Russian military activity in Crimea and eastern Ukraine, including what the US deemed a violation of a ceasefire by Moscow that led to the deaths of four Ukrainian soldiers last week.

"Russia's destabilizing actions undermine the de-escalation intentions that had been achieved through [last year's agreement]," chief Pentagon spokesman John Kirby said Wednesday. "Additionally, we are aware of Ukrainian military reports concerning Russian troop movements on Ukraine's borders."

Secretary of State Tony Blinken reaffirmed the "unwavering support" of the United States for Ukraine's territorial integrity in the face of "Russia's ongoing aggression in the Donbas and Crimea," according to a readout of his call with Ukrainian Foreign Minister Dmytro Kuleba Wednesday. Chairman of the Joint Chiefs of Staff Gen. Mark Milley also spoke to the top Ukrainian general Wednesday, while national security adviser Jake Sullivan spoke with his Ukrainian counterpart at the beginning of the week.

The Pentagon had grown increasingly concerned after military intelligence reports assessed that some 4,000 heavily armed Russian forces had been observed moving in Crimea, according to a US defense official. "It was not totally clear what they were up to," the official said, adding that the US now believes on further assessment it may have been part of a Russian military exercise. Part of that assessment was based on calls with Ukrainian officials who also viewed the Russian activity as an exercise.