(The Center Square) – U.S. Secretary of State Anthony Blinken said Friday that a Russian invasion of Ukraine could happen “at any time,” further heightening concerns in the region, which has seen military buildup in recent weeks.

“Simply put, we continue to see very troubling signs of Russian escalation, including new forces arriving at the Ukrainian border,” Blinken said during a news conference in Melbourne, Australia. “As we’ve said before, we’re in a window when an invasion could begin at any time. And to be clear, that includes during the Olympics.”

The president of Ukraine, though, has downplayed those concerns. Russia has denied claims it will invade, though it has amassed troops on the Ukrainian border and conducted a series of military exercises. Meanwhile, Biden has taken some criticism for his handling of the tension.

“The White House just announced that unless U.S. citizens evacuate in next 48 hours, Joe Biden’s policy is to leave American citizens behind in a war zone when Putin invades Ukraine,” said U.S. Rep. Elise Stefanik, R-N.Y.

The White House said Biden “held a secure video call with transatlantic leaders” Friday.

“The leaders expressed their concern about Russia’s continued build-up of military forces around Ukraine and reaffirmed their support for Ukraine’s sovereignty and territorial integrity,” the White House said in a statement. “They expressed their desire for a diplomatic solution to the crisis, and discussed recent engagements with Russia in multiple formats. The leaders agreed on the importance of coordinated efforts to deter further Russian aggression against Ukraine, including their readiness to impose massive consequences and severe economic costs on Russia should it choose military escalation, and to continue reinforcing the defensive posture on NATO’s eastern flank.”