WASHINGTON (Reuters) - President Donald Trump, under pressure from special counsel Robert Mueller’s investigation into Russia’s role in the 2016 U.S. election, probably has the power to pardon himself but does not plan to do so, his attorney Rudy Giuliani said on Sunday.

Asked whether Trump has the power to give himself a pardon, Giuliani said, “He’s not, but he probably does.” Giuliani added that Trump “has no intention of pardoning himself,” but that the U.S. Constitution, which gives a president the authority to issue pardons, “doesn’t say he can’t.”

Speaking on ABC’s “This Week” program, Giuliani added, “It would be an open question. I think it would probably get answered by, gosh, that’s what the Constitution says.”

Mueller is investigating whether Russia meddled in the presidential election and whether Trump’s campaign colluded with Moscow. Mueller, whose investigation already has led to criminal charges against Trump campaign aides including former campaign chairman Paul Manafort, is also looking into whether Trump unlawfully sought to obstruct the Russia investigation.

Both Russia and Trump deny collusion, and the president has denied obstructing the probe.

Giuliani noted that the political ramifications of a self-pardon could be severe. Giuliani told NBC’s “Meet the Press with Chuck Todd” that “the president of the United States pardoning himself would just be unthinkable. And it would lead to probably an immediate impeachment.”

Under the Constitution, a president can be impeached by the House of Representatives and then removed from office by the Senate.

The possibility of a self-pardon appeared to be raised in a Jan. 29 letter from Trump’s lawyers to Mueller, published by the New York Times on Saturday, arguing that the president could not have obstructed the probe given the powers granted to him by the Constitution.

“It remains our position that the President’s actions here, by virtue of his position as the chief law enforcement officer, could neither constitutionally nor legally constitute obstruction because that would amount to him obstructing himself, and that he could, if he wished, terminate the inquiry, or even exercise his power to pardon if he so desired,” Trump’s lawyers wrote.

FILE PHOTO: U.S. President Donald Trump look on as he welcomes South Korea's President Moon Jae-In in the Oval Office of the White House in Washington, U.S., May 22, 2018. REUTERS/Kevin Lamarque /File Photo

The letter did not explicitly describe the possibility of Trump pardoning himself.

Whether Trump may pardon himself is a matter of some debate.

A Justice Department memo dated four days before former President Richard Nixon resigned in 1974 during the Watergate political corruption scandal took the view that “under the fundamental rule that no one may be a judge in his own case, the President cannot pardon himself.”

House Majority Leader Kevin McCarthy, a Republican, made clear he did not think Trump or any other president should pardon himself. “I don’t think a president should pardon themselves,” he told CNN’s “State of the Union.”

‘MINOR LEGAL ARGUMENT’

Former Manhattan U.S. Attorney Preet Bharara, fired by Trump last year along with numerous other federal prosecutors, said it would be “outrageous” for a sitting president to pardon himself and that doing so would represent “almost self-executing impeachment.”

“Whether or not there is a minor legal argument that some law professor somewhere in a legal journal can make that the president can pardon, that’s not what the framers could have intended,” Bharara said on said on CNN’s “State of the Union” program, referring to the authors of the Constitution.

Trump has not been shy about using his pardon power.

The president on Thursday pardoned conservative commentator and filmmaker Dinesh D’Souza, who pleaded guilty in 2014 to U.S. campaign finance law violations.

Trump also said he was considering pardoning lifestyle maven Martha Stewart and commuting the prison sentence of former Illinois Governor Rod Blagojevich, convicted of corruption charges. Critics accused Trump of subverting the rule of law.

Giuliani told ABC it is an “open question” whether Trump would sit for an interview with Mueller but that the president’s lawyers were leaning against having him testify.

Giuliani also said the president’s legal team planned to challenge any potential subpoena from Mueller’s office as harassment or as unnecessary because the White House has turned over more than a million documents and several witnesses.

Trump took to Twitter on Sunday to again rage against the FBI and Justice Department, saying he would not have hired Manafort if he had been told Manafort was already under investigation.

“As only one of two people left who could become President, why wouldn’t the FBI or Department of ‘Justice’ have told me that they were secretly investigating Paul Manafort (on charges that were 10 years old and had been previously dropped) during my campaign? Should have told me!” Trump tweeted.

“Paul Manafort came into the campaign very late and was with us for a short period of time ... but we should have been told that Comey and the boys were doing a number on him, and he wouldn’t have been hired!” Trump wrote, referring to former FBI Director James Comey, who Trump fired last year.