Russia's claims it was pulling forces back from the border are false, U.S. Secretary of State Antony Blinken said in a statement on Friday, adding that "on the contrary, we see additional forces going to the border including leading edge forces that would be part of any aggression."

Blinken also said that everything Washington has seen happening on Russia's border with Ukraine in the past 24 to 48 hours is part of a scenario of creating false provocations designed to elicit a response.

The U.S. top diplomat was speaking at the Munich Security Conference alongside German Foreign Minister Annalena Baerbock.

Earlier on the same day, the U.S. ambassador to the Organization for Security and Co-operation in Europe (OSCE) Michael Carpenter said that Russia's buildup of military personnel threatening Ukraine probably totals up to 190,000 during a meeting on the Ukraine crisis.

"We assess that Russia probably has massed between 169,000-190,000 personnel in and near Ukraine as compared with about 100,000 on Jan. 30," Michael Carpenter told the meeting, which Russia did not attend. "This is the most significant military mobilization in Europe since World War II."

U.S. Defense Secretary Lloyd Austin, while in Poland on Friday, warned that a Russian invasion of Ukraine could trigger an exodus of people fleeing toward the European Union.

"If Russia further invades Ukraine, Poland could see tens of thousands of displaced Ukrainians and others flowing across its border trying to save themselves and their families from the scourge of war," he said alongside his Polish counterpart Mariusz Blaszczak in Warsaw.

Washington has estimated that some 30,000 Russian troops have been deployed at neighboring Belarus as part of joint exercises that are due to run until Sunday.

Those drills as well as other large-scale exercises near Ukraine have fueled concerns in European capitals and Washington that Moscow is preparing an attack on its neighbor.

Russia has denied any plans and accused Ukraine of breaching cease-fire agreements in the east of the country, where the army is fighting pro-Moscow separatists.