The U.S. side is concerned about recent escalation in eastern Ukraine.
The U.S. Department of Defense, or the Pentagon, says it is "aware of Russian troop movements" on Ukraine's borders and this issue is being discussed with NATO allies.
"We're concerned about recent escalations of Russian aggression in eastern Ukraine, including violations of the July 2020 ceasefire that led to the deaths of 40 [sic] Ukrainian soldiers on the 26th of March (according to Ukrainian military reports, four soldiers were killed on that day – the translator's note) and the wounding of two others," Pentagon press secretary John Kirby said at a press briefing on March 31, 2021, answering a question why the U.S. troops in Europe have gone on a heightened warning status.
According to him, Russia's destabilizing actions undermine the de-escalation intentions that had been achieved through an OSCE-brokered agreement back in July of last year.
"Additionally, we are aware of Ukrainian military reports concerning Russian troop movements on Ukraine's borders," the official said.
He said the U.S. was discussing its concerns about this increase in tensions and ceasefire violations and regional tensions with NATO allies.
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"Mr. Sullivan affirmed the United State's unwavering support for Ukraine's sovereignty, territorial integrity, and Euro-Atlantic aspirations in the face of continued Russia aggression," Kirby said.
Answering a question whether the secretary is worried that Russia could be preparing to further its incursion into Ukraine, he said: "We obviously don't want to see any more violations of Ukrainian territory. I'm not going to speak to intelligence matters."