The United States does not believe Russian leader Vladimir Putin has made a "final decision" on invading Ukraine, as Washington announced plans for the Pentagon chief to visit Europe amid mounting concerns over the continent's security.

"We still don't believe that some final decision has been made," Pentagon spokesman John Kirby told reporters. However, he also told them "military action could happen any day." 

This comes after President Biden "predicted" Saturday that Russia would attack Ukraine on February 16, while experts argued on the interpretation of intelligence reports.

According to Kirby, Defense Secretary Lloyd Austin will be leaving for Europe on Tuesday, where he will hold meetings at NATO's headquarters in Brussels and then go to Poland and Lithuania, where the US deployed thousands of troops.

No sign of de-escalation

Washington asserted that it has seen no "tangible sign of de-escalation" at the Russian border with Ukraine.

"It is a distinct possibility, perhaps more real than ever before, that Russia may decide to proceed with military action, with new Russian forces continuing to arrive at the Ukrainian border," State Department spokesman Ned Price told reporters. 

"An invasion, as we have said, could begin at any time," he added, again contradicting US "intelligence" that suggested Russia would "invade" on February 16.

As tensions rise with the US-predicted d-day being around the corner, the Pentagon put China on blast over its "tacit support" for Russia on Ukraine, saying it was "deeply alarming".

Russian Foreign Ministry Spokesperson Maria Zakharova on Sunday accused Washington of continuing to spread lies about Ukraine, explaining that US politicians continue to lie and create pretexts to attack civilians around the world.

More than 1,000 experts confirmed in a report issued after the invasion of Iraq that no weapons of mass destruction were found in this country, she stressed. 

The Kremlin had said during a call between President Putin and Biden the former denounced the false information about the "Russian invasion" in Ukraine and told the US president that "the West is not putting enough pressure on Ukraine to implement the Minsk agreements."