Washington is just days away from the start of the first impeachment trial in over two decades, but congressional leaders remain at odds over what exactly it will look like.

Even after House Speaker Nancy Pelosi, D-Calif., ended her unofficial filibuster of the process last Friday and committed to sending the impeachment articles to the Senate, Republican lawmakers are continuing to have discussions over whether the trial should feature a new round of witness testimony. Some GOP lawmakers, meanwhile, are aiming for a quick verdict and President Trump himself has started to publicly argue that the case simply should be dismissed.

PELOSI: HOUSE WILL MOVE TO TRANSMIT IMPEACHMENT ARTICLES NEXT WEEK

The timing for all of this remains fluid. While Pelosi could prepare to send the articles to the Senate as early as Tuesday, a congressional source told Fox News that the speaker could wait until later in the week.

The trial would not begin the moment Pelosi transmits the articles – alleging abuse of power and obstruction of Congress – to the Senate either. A Senate GOP aide told Fox News that there would be three to four days of pre-trial preparations.

The aide told Fox News that part of the pre-trial prep would include the swearing-in of senators and U.S. Chief Justice John Roberts, briefings from the House managers and President Trump’s legal team, and a debate and vote on the resolution that would lay out the parameters for the trial.

How the trial would proceed remains an open question.

Senate Majority Leader Mitch McConnell, R-Ky., has repeatedly said that the resolution to govern the impeachment trial in the Senate would mirror the one used for then-President Bill Clinton’s impeachment trial in 1999 — setting a time frame for the trail to begin, with the opportunity for lawmakers to determine how to proceed on potential witness testimony and additional documents later, after both the president’s defense and the prosecution make their opening statements.

McConnell has insisted that he has the votes to pass the organizing resolution and begin the trial, before committing to witness testimony. In impeachment, most resolutions can pass with a simple majority. To remove the president from office, though, there must be 67 votes.

But while some Republicans have argued against the possibility of new witness testimony, Sen. Susan Collins, R-Maine, said last week that she was working with a “fairly small group” of GOP senators to ensure that witnesses can be called in Trump’s trial.

GOP SENATORS MOVE TO DISMISS ARTICLES OF IMPEACHMENT AMID BATTLE WITH PELOSI

“I have had many discussions with some of my Republican colleagues on how we can adhere as closely as practical to the precedent for conducting the impeachment trial of President Clinton, which included as a third stage the decision on whether to call witnesses,” Collins said last week. “I am hopeful that we can reach an agreement on how to proceed with the trial that will allow the opportunity for witnesses for both the House managers and the President’s counsel if they choose to do so.”

She added: “It is important that both sides be treated fairly.”

Democrats are keen to see the Senate call in high-level witnesses who did not testify on the House side — especially former National Security Adviser John Bolton, who recently offered to come forward, only for Trump to indicate he could claim executive privilege to stop it.

Trump has gone further in recent days, suggesting over the weekend the Senate should bypass a trial and dismiss the articles.

“Many believe that by the Senate giving credence to a trial based on the no evidence, no crime, read the transcripts, ‘no pressure’ Impeachment Hoax, rather than an outright dismissal, it gives the partisan Democrat Witch Hunt credibility that it otherwise does not have,” Trump tweeted on Sunday. “I agree!”

White House Press Secretary Stephanie Grisham on Monday doubled down on the president's suggestion.

"I think the president's communicating that there should be a dismissal because he did nothing wrong," Grisham said on Fox News' "Outnumbered Overtime." "The president shouldn't have to go through this. He did nothing wrong. He released transcripts, willingly, because he did nothing wrong, and so, he's made that clear all along."

She added: "Obviously, he would want a dismissal of everything. But at the end of the day, if it does go to the Senate for a trial, he does want it to be fair, which is all he deserves."

The president’s tweet came just days after a group of Republican senators, including McConnell, signed onto a resolution put forth by Sen. Josh Hawley, R-Mo., that would allow the chamber to dismiss impeachment against Trump should Pelosi continue to hold onto the articles.

That resolution, though, became somewhat moot after Pelosi announced on Friday that she would send the articles and announce House managers to prosecute the case.

Still, Trump-allied GOP Sen. Lindsey Graham said over the weekend that he anticipates this trial would be over in a matter of days.

The president, meanwhile, slammed Pelosi and Democrats on Monday, calling into question their demands for fairness by citing the process on the House side.

In the House impeachment inquiry, largely led by House Intelligence Committee Chairman Adam Schiff, D-Calif., the Democrats had final say over witnesses. Democrats did, however, give Republican lawmakers the ability to subpoena witnesses with the concurrence of Democratic committee chairs and members.

"'We demand fairness' shouts Pelosi and the Do Nothing Democrats, yet the Dems in the House wouldn't let us have 1 witness, no lawyers or even ask questions. It was the most unfair witch-hunt in the history of Congress!" he tweeted Monday.

The next step for Pelosi will be to determine who will serve as House managers to prosecute the case against the president in the Senate trial.

Last month, bipartisan sources told Fox News that several names have been floated to make the case for the president’s removal.

Likely candidates include House Judiciary Committee Chairman Jerry Nadler, D-N.Y., whose panel drafted the articles of impeachment (abuse of power and obstruction of Congress); Schiff, who led much of the impeachment inquiry out of his committee with dramatic hearings to develop the case against the president; House Democratic Caucus Chairman Hakeem Jeffries, D-N.Y.; and Rep. Jamie Raskin, D-Md., a constitutional lawyer.

Other possible candidates include Democrats who were more outspoken during the impeachment hearings, like Rep. David Cicilline, D-R.I., and Eric Swalwell, D-Calif.

Sources told Fox News that other names being floated include Reps. Pramila Jayapal, D-Wash.; Val Demings, D-Fla., who served as the first female police chief in Orlando; and Zoe Lofgren, D-Calif., who was involved in the impeachment of former President Bill Clinton and was a staffer during the congressional investigation into former President Richard Nixon.

During Clinton’s impeachment in 1999, there were 13 House impeachment managers. A source familiar with the planning told Fox News that Pelosi is expected to appoint fewer than that.