The Ukrainian government urged citizens on Saturday to stay calm and united, saying the armed forces are ready to repel any attack on the country amid concern that Russia may be poised to invade.
"It is now critical to remain calm and united within the country, and avoid actions that undermine stability and sow panic," the Foreign Ministry said in a statement.
"Ukraine's Armed Forces are constantly monitoring developments and are ready to repel any encroachment on the territorial integrity and sovereignty of Ukraine," it added.
Russia has massed more than 100,000 troops near its border with Ukraine and the United States said on Friday an invasion could come at any time. Washington also urged its citizens in Ukraine to leave as soon as possible, a call echoed by countries including Britain, Japan and Australia.
Moscow denies plans to invade, saying it is defending its own security interests against aggression by NATO allies.
US President Joe Biden and his Russian counterpart Vladimir Putin were due to speak on Saturday. US Secretary of State Antony Blinken also said he would talk to Russian Foreign Minister Sergei Lavrov.