WASHINGTON — Sen. Claire McCaskill, D-Mo., who fired off one of the harshest criticisms of Attorney General Jeff Sessions over his meetings with a Russian ambassador, faced blowback herself Thursday when the senator's own tweets contradicted her claim that she never had met the ambassador.

McCaskill called on Sessions to resign, saying he "misled the Senate" about his contact with Russian officials during the 2016 election campaign.

The Washington Post reported Wednesday night that Sessions met twice with the Russian ambassador to the U.S. last year. During his confirmation hearing to become President Trump's top law enforcement official, Sessions said he had no contact with Russian officials and did not know anything about reported contacts between Trump's campaign advisers and allies of Russian President Vladimir Putin.

“I’m not aware of any of those activities,” Sessions told the Senate Judiciary Committee during his January confirmation hearing. "I have been called a surrogate at a time or two in that campaign, and I did not have communications with the Russians.”

A spokeswoman for Sessions, in a statement responding to the Post story, said he did not disclose his meetings with the Russian ambassador because he was asked during the hearing about communications between Russia and the Trump campaign. His spokeswoman said Sessions' meetings with the Russian ambassador were held in his role as a senator and a member of the Armed Services Committee, not in his role as a top Trump campaign adviser.

McCaskill blasted that explanation.

“A good prosecutor would have known these facts were relevant to the questions asked,” McCaskill said in a statement Thursday morning. "It's clear Attorney General Sessions misled the Senate — the question is, why? I’ve been on the Senate Armed Services Committee for 10 years, and in that time, have had no call from, or meeting with, the Russian ambassador. Ever.

"That’s because ambassadors call members of Foreign Relations Committee," McCaskill added. "Attorney General Sessions should resign.”

McCaskill's statement that she never met with Russia's ambassador was immediately challenged by Charles C. Cooke, editor of National Review Online, a conservative news site. Cooke noted that McCaskill had tweeted about a 2013 meeting with Russia's top diplomat in the U.S.

Asked to explain, McCaskill said the meeting on adoption was with about a dozen other senators. She said she never had been contacted by the Russian ambassador nor had a one-on-one meeting with him.

"The Russian ambassador has never called me. The Russian ambassador has never requested a meeting. I have never met with the Russian ambassador one-on-one," McCaskill said.  "I went to a meeting on adoptions, and he was there. But it was a bunch of senators. And it had nothing to do with the Armed Services Committee."