House Democrat wants ethics probe of Republican congressman's Michael Cohen tweet ahead of public testimony Michael Cohen testifies before the House Oversight Committee on Wednesday.

Rep. Kathleen Rice, D-N.Y., asked the House Ethics Committee Tuesday to investigate a tweet from a Republican congressman about Michael Cohen ahead of his public testimony before Congress, a move that could prompt an official investigation.

In a letter to the panel, Rice said she believes Rep. Matt Gaetz's controversial tweet Tuesday evening, which implied alleged details about Cohen's romantic life could come out during Cohen’s public testimony, constituted witness tampering.

Gaetz, a self-described Trump loyalist, tweeted: “Hey @MichaelCohen212 - Do your wife & father-in-law know about your girlfriends? Maybe tonight would be a good time for that chat. I wonder if she’ll remain faithful when you’re in prison. She’s about to learn a lot...”

"As a former District Attorney and federal prosecutor, I believe this statement is in violation of 18 U.S. Code 1512, which clearly defines witness tampering and intimidation," she wrote in the letter obtained by ABC News. "According to the Department of Justice ... this statute applies to proceedings before Congress."

Rice, who encouraged the committee to refer the matter to the Justice Department after an investigation, discussed the tweet with Gaetz on the House floor Tuesday evening, according to a source familiar with their conversation.

Under its rules, the House ethics panel could launch an investigation into the matter from the referral. A committee official declined to comment on Rice's referral.

After a committee investigation, the panel could eventually recommend the House vote to reprimand, censure or fine Gaetz, Bryson Morgan, a former investigative counsel for the House of Representatives Office of Congressional Ethics, told ABC News.

The panel could also recommend expulsion, which would require a two-thirds majority of the chamber.

Gaetz was questioned by reporters moments after his tweet and why he wrote it, saying “the tweet speaks for itself."

Gaetz was asked if the tweet should be perceived as a threat telling reporters, “Absolutely not. We’re witness testing not witness tampering. And when witnesses come before Congress their truthfulness and voracity ought to be tested and we have the opportunity.”

Gaetz apologized in a later tweet around midnight Wednesday and said he planned to delete the inflammatory Cohen tweet.

"Speaker, I want to get the truth too. While it is important 2 create context around the testimony of liars like Michael Cohen, it was NOT my intent to threaten, as some believe I did," he said in a response to a tweet from House Speaker Nancy Pelosi, D-Calif. "I’m deleting the tweet & I should have chosen words that better showed my intent. I’m sorry."

Lanny J. Davis, an attorney for Michael Cohen, said: "We will not respond to Mr. Gaetz’s despicable lies and personal smears, except to say we trust that his colleagues in the House, both Republicans and Democrats, will repudiate his words and his conduct. I also trust that his constituents will not appreciate that their congressman has set a new low — which in today’s political culture is hard to imagine as possible.”

The tweet from Gaetz was a stunning attack from a member of Congress ahead of public testimony.

“I think it’s enough to warrant an investigation. This is knowingly using intimidation ... with the intent to influence or delay or prevent the testimony,” said Melanie Sloan, a former federal prosecutor, senior adviser to American Oversight, a government watchdog group referring to the federal code. “This guy could be charged with witness tampering.”

Asked for any proof about his allegations against Cohen, Gaetz told ABC News "tune in tomorrow and find out." Gaetz is not a member of the House Oversight Committee, which will question Cohen tomorrow for his first public hearing.

Cohen has been testifying before members and staff of the Senate Intelligence Committee behind closed doors since first thing Tuesday morning.

The longtime Trump Organization employee plead guilty to lying to Congress as well as financial crimes including bank and tax fraud late last year. Cohen also pleaded guilty to campaign finance violation for payments made to adult film star Stormy Daniels during the 2016 presidential campaign.

A source familiar with his public testimony plans for Wednesday told ABC News Cohen is expected to publicly accuse President Trump of potentially committing a crime while in office. The accusation, according to the source, is related to Trump's alleged repayment of money to Cohen for his deal with Daniels. Trump has denied Daniels' claim but has admitted to the reimbursement.

Trump has denied the affair alleged by Daniels and another accusation from former Playboy model Karen McDougal, and has previously said the payment amounted to nothing more than a “simple private transaction,” and that they do not qualify as campaign finance violations.

ABC News' Karma Allen contributed to this report.