US Secretary of State John Kerry said on Wednesday that Russia must be "very careful" in the decisions it makes on Ukraine, and that the country's President should remember "this is not Rocky IV".
"I think Russia needs to be very careful in the judgments that it makes going forward here," he told US TV network NBC News.
"We are not looking for confrontation. But we are making it clear that every country should respect the territorial integrity here, the sovereignty of Ukraine.
"Russia has said it would do that and we think it's important that Russia keeps its word," he added.
Mr Kerry said that Russian President Vladimir Putin should "listen carefully to Ukrainians who have voiced their desire for change," and reiterated that the US does not view its relationship with Russia as a "sort of continuation of the Cold War."
"This is not Rocky IV," he said, referring to the 1990 film depicting a battle between East and West, in which Rocky Balboa fights then-Soviet Union boxer Ivan Drago.
"Believe me. We don't see it that way", he added.
His comments come after Mr Putin ordered an urgent drill to test the combat readiness of its military forces amid tensions with the West over Ukraine.
According to the Defence Minister Sergei Shoigu, the manoeuvres commencing on Friday will last four days.
He added the exercise will involve ships of the Baltic and the Northern Fleets and the air force.
Shoigu's statement made no reference to Ukraine, where tensions remain high following the ousting of Russia-backed President Viktor Yanukovych.
Mr Kerry said he would "decline to speculate" on the whereabouts of Mr Yanukovych or whether he should be prosecuted for war crimes.
"We need to work together in what does not have to be a zero sum game to provide the capacity of the people of Ukraine to choose their future," Kerry said. "That's all that's at stake."
- The Independent