Oregon Sen. Jeff Merkley took to Twitter early Friday calling on President Donald Trump to resign amid reports that Trump had instructed his former lawyer, Michael Cohen, to lie to Congress about his business interests in Moscow.

Merkley was among a chorus of Congressional Democrats claiming that Trump may have committed an impeachable offense. “If this report of Trump suborning false testimony is confirmed, then Trump committed a felony and must resign or be impeached,” Merkley tweeted.

The bombshell report published Thursday evening by BuzzFeed attributed the claims to two unnamed members of Special Counsel Robert Mueller’s team. “The special counsel’s office learned about Trump’s directive for Cohen to lie to Congress through interviews with multiple witnesses from the Trump Organization and internal company emails, text messages, and a cache of other documents,” the article said. “Cohen then acknowledged those instructions during his interviews with that office.”

Merkley was among the first to call for Trump’s resignation, along with U.S. Rep. Joaquin Castro, D-Texas, and Sen. Chris Murphy, D-Conn.

The bombshell sputtered later in the day when Mueller’s office disputed the Buzzfeed report. “BuzzFeed’s description of specific statements to the Special Counsel’s Office, and characterization of documents and testimony obtained by this office, regarding Michael Cohen’s Congressional testimony are not accurate,” said Peter Carr, a spokesman for Mueller’s office, in a statement.

Trump has consistently denied any wrongdoing, calling the Mueller investigation a “witch-hunt." He’s also criticized much of the media which he claims is out to get him.

Cohen pleaded guilty in late November to lying to Congress. He cut a deal with Mueller’s team to cooperate. Trump then began referring to his former fixer as a “rat.”

“Remember, Michael Cohen only became a “Rat” after the FBI did something which was absolutely unthinkable & unheard of until the Witch Hunt was illegally started,” Trump tweeted on Dec. 18. “They BROKE INTO AN ATTORNEY’S OFFICE!”

Mueller’s initial charter was to investigate whether Russians conspired to interfere in the 2016 Election to get Trump elected. At the core of the current matter is whether Trump was pursuing his personal real estate interests in Moscow even as he was running for the presidency. Trump’s real estate organization was looking to build a $300 million office tower in Moscow. Cohen told Congress the deal was dead by January 2016, a claim that’s been widely discredited.

Cohen, who is scheduled to testify before Congress next month, has acknowledged that the conversations he had with Trump about the project exceeded the three short briefings he testified to, and that he also held more extensive discussions about it with other members of the Trump family. The sources said Cohen gave Trump’s children “very detailed updates.”

As of Friday afternoon, Merkley had issued no new Tweet in light of the Mueller statement. By then, he’d moved on to the immigration issue, calling for an FBI investigation of Department of Homeland Security Secretary Kirstjen Nielsen.