Democrats in the U.S. House Judiciary Committee are expected to announce articles of impeachment against President Donald Trump on Tuesday, a lawmaker told multiple U.S. media outlets.

Elliot Engel, the House Foreign Affairs Chairman, told reporters that the articles of impeachment were likely be unveiled at a news conference on Tuesday morning.

It is unclear how many articles will be introduced and on what charges the articles will be based.

Democrats say that Trump withheld military aid to Ukraine as part of a pressure campaign to get Ukrainian President Volodymyr Zelensky to investigate Trump’s domestic political rival Joe Biden and conspiracy theories related to the 2016 presidential election.

According to the Democrats, Trump abused power and committed bribery, accusations which Trump denies.

Once the Democrats’ articles of impeachment are formally introduced, they are likely to go through changes before leaving the House Judiciary Committee and are put up for a general vote.

If the Democrat-controlled House votes in favour of the impeachment articles, then the process moves to the Republican-controlled Senate, where Trump’s supporters have promised to defend the president.

On Monday Democrats held a public hearing summing up their case against the president.

House Judiciary Committee staff lawyers for majority Democrats laid out evidence for impeachment over Trump’s dealings with Ukraine earlier this year, while a committee lawyer for minority Republicans rebutted the claims in sometimes heated exchanges.

“We are here today because Donald J Trump, the 45th president of the United States, abused the power of his office, the American presidency, for his political and personal benefit,” Daniel Goldman, a lawyer for Democrats on the House Intelligence Committee, said in his opening statement.

Democrats say a back-and-forth during a July 25 call between Trump and Zelensky showed a “quid pro quo” that put Trump’s own personal political interests over U.S. national security.

Trump has vehemently denied any wrongdoing, and on Monday he tweeted about the hearing, citing a comment from Zelensky that Trump did nothing wrong.

“If the Radical Left Democrats were sane, which they are not, it would be case over!” he tweeted.

Republicans on the committee said that the evidence presented since the inquiry was announced in September, based on a whistle-blower’s report, was thin and the process used by the Democrats unfair.

But the Democrats’ lawyer for the Judiciary Committee told lawmakers that the evidence against Trump was “overwhelming” and revealed a “brazen” scheme.

Barry Berke said that impeaching him was an urgent matter because he could potentially repeat the behaviour.

“This is a big deal. President Trump did what a president of our nation is not allowed to do,” Berke said.

In addition to Goldman and Berke the committee heard testimony from Stephen Castor, a lawyer for Republicans on both committees.

He said that the process was “not warranted” based on the evidence and that a “compelling argument” to take a decision “out of the hands of the voters” was lacking.

The full House could vote on articles of impeachment as early as Friday.

The inquiry’s leaders have not yet named the specific impeachable offences they may vote on.

Once articles of impeachment are passed – as expected in the Democrats-dominated House – the articles would then move to the Republican-controlled Senate, where Democrats appear unlikely to rally enough Republicans to vote to remove Trump from office.

Democrats in the House appear undeterred by that reality.

Democrats have said that the matter is too important, citing it as an example of what the framers of the U.S. Constitution intended to stop when they gave Congress the ability to remove a president through impeachment.

Judiciary Committee Chairman Jerrold Nadler said in his opening statement that Trump “put himself before country” as monarchs of the past had done.

Nadler was forced to pound his gavel several times and warn Republican members not to interrupt as they bickered over procedural matters.

He also was forced to order a number of roll call votes to satisfy Republican demands, even once over a question of whether the committee should take a break.

Republicans complained bitterly about the timing of the impeachment process just a year before the next presidential election and said that the evidence didn’t show that impeachable offences had been committed.

Representative Douglas Collins complained that the Democrats had put the House in danger by abusing its power, saying that the hearings had been “all military,” and adding, “It’s a show”.