Washington: President Donald Trump on Tuesday angrily denounced the looming House votes to impeach him as a “Star Chamber of partisan persecution” by Democrats, describing the effort to remove him from office as an “attempted coup” that would come back to haunt them at the ballot box next year.

On the eve of the historic votes, Democrats reached a critical threshold, gathering majority support to impeach Trump, as the president raged against the proceedings. In an irate and rambling six-page letter to Speaker Nancy Pelosi, Trump portrayed himself as the victim of enemies determined to destroy his presidency with false accusations.

“This is nothing more than an illegal, partisan attempted coup that will, based on recent sentiment, badly fail at the voting booth,” Trump declared, describing a process enshrined in the Constitution as an attempted government overthrow.

“History will judge you harshly as you proceed with this impeachment charade,” he wrote.

In a missive full of unproven charges, hyperbole and long-simmering grievances against his own government — at one point, he referred to leaders of the FBI as “totally incompetent and corrupt” — Trump angrily disputed both of the impeachment charges: abuse of power and obstruction of Congress.

The letter ignored the extensive evidence uncovered during a two-month inquiry by the House Intelligence Committee, based in part on the testimony by members of his own administration. It found that Trump sought to pressure Ukraine to investigate his political rivals while holding back nearly $400 million (Dh14,690) in military assistance the country badly needed and a White House meeting for its president.

The charges accuse Trump of engaging in a corrupt scheme to enlist a foreign power for his own political benefit in the 2020 election, followed by an effort to conceal his actions by blocking congressional investigations. On Wednesday, the House is all but certain to approve them on nearly party-line votes, making him the third president ever to be impeached.

Past presidents have offered contrition as they stared down looming House impeachment votes. President Bill Clinton issued a personal apology from the White House Rose Garden in 1998, biting his lip and saying he was “profoundly sorry” for his actions in the Monica Lewinsky affair days before the House voted to impeach him. President Richard M. Nixon resigned his office in 1974 rather than face the vote at all.

Defiant and unrepentant

But Trump was defiant and unrepentant Tuesday. He accused Pelosi and her party of fabricating lies, saying that the speaker and Democrats were possessed by “Impeachment Fever” and vowing that he and the Republican Party would emerge stronger after he was vindicated in a Senate trial.

The president wrote that he knew his letter would not change the outcome. But he said that the document was “for the purpose of history and to put my thoughts on a permanent and indelible record.”

In her own message Tuesday evening to Democratic lawmakers, Pelosi made no reference to the president’s communication, instead urging her colleagues to “proceed in a manner worthy of our oath of office to support and defend the Constitution of the United States”.

Trump and Pelosi released their letters as Democrats began drafting rules for debate on the House floor. Meeting in a tiny hearing room just upstairs from the chamber, the House Rules Committee kicked off the broader House debate over the fate of Trump’s presidency.

“This scheme to corrupt an American presidential election subordinated the democratic sovereignty of the people to the private political ambitions of one man, the president himself,” said Rep. Jamie Raskin, Democrat-Maryland, a member of the Judiciary Committee. “It immediately placed the national security interests of the United States of America at risk.”

‘Unfair and illegitimate process’

Republicans responded with the same ferocity that has characterised their defence of Trump throughout the impeachment inquiry, insisting that the president had done nothing wrong and certainly nothing that warranted impeachment, and accusing Democrats of orchestrating an unfair and illegitimate process.

The Rules Committee voted along party lines Tuesday night to allow a total of six hours of debate over impeachment on the House floor Wednesday, divided equally among Republican and Democratic lawmakers.

As House Democrats moved methodically toward the votes, the Republican and Democratic leaders in the Senate clashed over the procedures that would guide an impeachment trial that is likely to begin early next year.

Sen. Mitch McConnell, Republican-Kentucky, the majority leader, rejected demands by Democrats to call four White House officials as witnesses. He said there was no reason now for the Senate to agree to take testimony from officials who might bolster Democrats’ case against the president. Later, in a strikingly public rejection of the oath senators take during an impeachment trial to “do impartial justice,” McConnell insisted he had no obligation to be even-handed in his handling of the proceeding.

“I’m not an impartial juror,” he told reporters. “This is a political process. I’m not impartial about this at all.”

Sen. Chuck Schumer, Democrat-New York, the minority leader, had requested in a letter to McConnell that the Senate take testimony during trial from four key figures, including Mick Mulvaney, the acting White House chief of staff, and John Bolton, a former national security adviser.

After McConnell’s rebuff, Schumer said that holding a trial without witnesses “would be an aberration”. In an interview, he added that the move would shirk the responsibility the Senate has to get to the truth about what occurred, and that it “eats away at the foundation of the republic”.

“The bottom line is that a trial with no witnesses, a trial with no documents is not a trial,” he said, adding, “We are going to do everything we can to get these documents and get these witnesses.”

The bitter exchange between the Senate leaders came as the most politically vulnerable House Democrats continued to announce their support for the impeachment charges.