"It's dangerous. It adds to the risk of miscalculation. It needs to be avoided," Blinken told a press briefing in Washington.

Pentagon spokesman John Kirby said meanwhile that the United States had postponed a planned test launch of a ballistic missile so as not to exacerbate tensions.

"In an effort to demonstrate that we have no intention in engaging in any actions that can be misunderstood or misconstrued, the secretary of defense has directed that our Minuteman III intercontinental ballistic missile test launch scheduled for this week be postponed," Kirby said.

"We did not take this decision lightly, but instead to demonstrate that we are a responsible nuclear power," he said.

"We recognize at this moment of tension how critical it is that both the United States and Russia bear in mind the risk of miscalculation and take steps to reduce those risks."