US Secretary of State Antony Blinken has called on Russia to take a "diplomatic and peaceful path" as fears mount of a new invasion of Ukraine.
An estimated 100,000 Russian troops have been deployed near Ukraine's borders and Mr Blinken, visiting Kyiv, said Russian plans were in plans to beef them up at short notice.
Russia has repeatedly denied planning to invade neighbouring Ukraine.
But senior US officials say Moscow could attack at "any point".
Mr Blinken will meet his Russian counterpart in Geneva on Friday, after talks with European allies in Berlin.
Ahead of his visit to Kyiv, senior state department officials indicated that Russian Foreign Minister Sergei Lavrov may be offered the option of a "diplomatic off-ramp" in Geneva. The White House said no option was off the table.