WASHINGTON — Senate Majority Leader Mitch McConnell, R-Ky., said Tuesday that the Senate's trial of President Donald Trump will likely begin Tuesday.

McConnell said the start date depends on House Speaker Nancy Pelosi's sending the two articles of impeachment to the Senate on Wednesday, as she said she would if the House approved. He said the Senate would begin preparations this week.

"The House is likely to finally send the articles over to us tomorrow, and we'll be able to — we believe if that happens — in all likelihood, go through some preliminary steps here this week, which could well include the chief justice coming over and swearing in members of the Senate and some other kind of housekeeping measures," McConnell said after a closed-door luncheon with members of the Senate Republican Conference. John Roberts, chief justice of the United States, will preside over the trial.

McConnell reiterated that he has the support of 53 Republican senators on an initial resolution to outline how to move forward. The first measure, he said, would set up the arguments from both parties — the prosecution and the defense — and then provide for a period in which senators could submit written questions.

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"Then after that," he said, "the more contentious issue of witnesses would be addressed by the Senate."

In response to a question, McConnell appeared open to the idea of calling Hunter Biden, the son of former Vice President Joe Biden, as a witness should Democrats call former White House national security adviser John Bolton.

"I can't imagine that only the witnesses that our Democratic colleagues would want to call will be called," he said.

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A simple majority of the Senate is required to determine which witnesses are called. Asked whether the White House might block witnesses from appearing, McConnell said: "Who knows who will employ what kind of legal devices? I have no idea."

Trump signaled last week that he would seek to prevent Bolton, a key figure in the impeachment saga who did not testify in the House's inquiry, from appearing at the Senate trial.

Asked in a Fox News interview why he would not let Bolton testify, Trump said, "I have no problem, other than one thing: You can't be in the White House as president — future, I'm talking about future, many future presidents — and have a security adviser, anybody having to do with security, and legal and other things."

Asked whether he would invoke executive privilege, Trump said, "Well, I think you have to, for the sake of the office."

Bolton has said he would testify if the Senate subpoenaed him.

Regarding Trump's calls for the Senate to dismiss the House's case, McConnell made it clear that he does not have the votes.

"There's little or no sentiment in the Republican conference for a motion to dismiss. Our members feel that we have an obligation to listen to the arguments," he said.

Trump tweeted over the weekend: "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. I agree!"

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. I agree! — Donald J. Trump (@realDonaldTrump) January 12, 2020

Asked whether there could be a trial without witnesses, McConnell deflected the question and blamed House Democrats.

"If you look at the House product, you've really got to wonder what the definition of a fair trial is," he said. "They did almost nothing of what you would expect the House to do in order to set up this case to be considered by the Senate."

Meanwhile, Senate Minority Leader Chuck Schumer, D-N.Y., said he was "pleased" that some Republicans were coming around to the Democrats' position of wanting witnesses and documents.

"If you want the truth, you have to have witnesses, you have to have documents. Who has ever heard of a trial without witnesses and documents?" Schumer said.

"Let's remember what this trial is for — for a president, any president, to threaten a foreign country with the cutoff of aid unless they interfere in our elections is what the Founding Fathers felt is one of the worst abuses a president can have," he said. "These charges are deep and serious, and all we can say is we join the American people in wanting the truth."

Schumer said he has not seen the initial Senate resolution to set up the trial.