The United States urges its citizens not to travel to Ukraine, and all Americans already in the country are urged to leave Ukraine as soon as possible due to the increased threat of Russian invasion and the COVID-19 pandemic, according to travel advisories posted on the U.S. Embassy website in Ukraine.

"Do not travel to Ukraine due to the increased threats of Russian military action and COVID-19; those in Ukraine should depart now via commercial or private means," the recommendations say.

"If remaining in Ukraine, exercise increased caution due to crime, civil unrest, and potential combat operations should Russia take military action," they note.

"There are continued reports of a Russian military build-up on the border with Ukraine, indicating potential for significant military action against Ukraine. The security conditions, particularly along Ukraine's borders, in Russia-occupied Crimea, and in Russia-controlled eastern Ukraine, are unpredictable and can deteriorate with little notice," the recommendations say.

They clarify that the U.S. government will not be able to evacuate U.S. citizens in the event of Russian military action anywhere in Ukraine.

"Military action may commence at any time and without warning and would also severely impact the U.S. Embassy's ability to provide consular services, including assistance to U.S. citizens in departing Ukraine," the recommendations say.