Private citizens of Ukraine were warned to leave in the midst of the tension with Russia.

The Biden administration is evacuating all remaining embassy personnel from Ukraine, which could come under attack by invading Russian forces as soon as this week, according to high-ranking officials.

Ukrainian President Volodymyr Zelensky posted a warning on social media that Russia will attack on Wednesday, February 16 and called for that to be a "Day of Unity" in Ukraine.

Biden administration officials also said they are seeing indications that an offensive could be imminent.

"We have seen over the course of the past 10 days a dramatic acceleration in the buildup of Russian forces," said National Security Advisor Jake Sullivan on Sunday. "And the disposition of those forces in such a way that they could launch a military action, essentially at any time."

President Biden spoke on the phone with Russian President Vladimir Putin for an hour this weekend, but the call reportedly produced no breakthroughs.

Russia has demanded a halt in NATO's eastward expansion and a commitment that Ukraine will not be offered NATO membership.

Both of those demands have been rejected by the U.S. and its European allies.

A small diplomatic window appears to still be open, as Russian Foreign Minister Sergei Lavrov recommended to President Putin on Monday that he continue with and expand talks with the West.

German Chancellor Olaf Scholz, who met with President Biden at the White House a week ago, met with President Zelensky on February 14 in Kyiv. He is scheduled to meet with Putin in Moscow on February 15.

"As far as we're concerned, the United States of America, diplomacy is still open and available," said the NSA's Sullivan, "but if Russia chooses to move, we're prepared to respond."

No member of Oklahoma's congressional delegation has more foreign relations experience than Sen. Jim Inhofe (R-OK), the current ranking member of the Senate Armed Services Committee.

Sen. Inhofe said he's doubtful Putin will ultimately take a diplomatic option.

"We know about Putin, we know what his capabilities are," said Inhofe in an interview last week, "I’m one of ‘em who believes that he is going to strike, and there’s going to be a level of warfare."

Inhofe has criticized the administration for "responding to Putin too slowly."

Inhofe agrees with the decision to send lethal aid to Ukraine and U.S. troops to Eastern Europe.

He said that action of aid sends an important message to the rest of Eastern Europe, which he said is very concerned and watching this very closely.

"I was standing there with the leadership of Romania," said Inhofe, recalling his trip there 9 months ago. "They said, 'This is—if this happens with Ukraine, we'll be next' and you’ve heard the ‘we will be next’ from several other countries."