Attorney General William P. Barr told the Associated Press on Tuesday that he has “not seen fraud on a scale that could have effected a different outcome in the election,” undercutting claims that President Trump and his allies have made — without evidence — of widespread and significant voting irregularities.

In an interview, Barr suggested the FBI and Justice Department have looked into some fraud claims, and seemed to take particular aim at one, by attorney Sidney Powell, who alleged a grand conspiracy involving election software changing voting tallies.

“There’s been one assertion that would be systemic fraud and that would be the claim that machines were programmed essentially to skew the election results. And the DHS and DOJ have looked into that, and so far, we haven’t seen anything to substantiate that,” Barr told the Associated Press, referring to the departments of Homeland Security and Justice.

Though, privately, Justice Department officials have for weeks said that there was not evidence to substantiate the claims of Trump and his allies, Barr’s publicly breaking with the president is particularly significant.

Before the election, Barr had warned repeatedly and forcefully about possible fraud that might come with mass mail-in voting, echoing the president’s attacks on the practice. Afterward, he reversed long-standing Justice Department policy and authorized prosecutors to take overt steps to pursue allegations of “vote tabulation irregularities” in certain cases before results are certified — drawing criticism that he was trying to magnify Trump’s claims of widespread voter fraud.

That memo, though, only authorized actions in cases which could change the outcome of the election, and officials have previously told The Washington Post they were aware of no such investigations or evidence that would warrant them.

In the interview, Barr said that most of the claims of fraud that had come to the department were “very particularized to a particular set of circumstances or actors or conduct. They are not systemic allegations. And those have been run down; they are being run down.”

“Some have been broad and potentially cover a few thousand votes,” he said. “They have been followed up on.”

In a statement, Rudolph W. Giuliani, Trump’s personal attorney, and Jenna Ellis, a legal adviser to the campaign, said, “With all due respect to the Attorney General, there hasn’t been any semblance of a Department of Justice investigation.” The two lawyers have been leading Trump’s effort to attack the results of the election, and though they have appeared with Powell, they have said publicly she is not formally working for Trump. Powell did not return an email seeking comment.

In recent weeks, officials said, Trump has been speaking with Giuliani and Ellis extensively, believing his other advisers are too skeptical about his claims or too pessimistic about his chances.

“Nonetheless, we will continue our pursuit of the truth through the judicial system and state legislatures, and continue toward the Constitution’s mandate and ensuring that every legal vote is counted and every illegal vote is not,” their statement said. “Again, with the greatest respect to the Attorney General, his opinion appears to be without any knowledge or investigation of the substantial irregularities and evidence of systemic fraud.”

Since it became clear that Joe Biden won the election, Trump and his allies have sought to discredit the results, mounting unsuccessful court challenges and publicly decrying what they claim to be fraud and other irregularities.

A person who spoke with Trump on Monday said he was railing against governors in Republican states — particularly in Georgia and Arizona — who would not back up his claims of fraud and were proceeding to certify results. Barr’s comment takes away another valuable ally in his cause that is expected to go nowhere, but Trump nevertheless is unlikely to give it up until at least after the electoral college votes Dec. 14, this person said.

Even as news broke of Barr’s statements to the Associated Press, Trump was tweeting about “hundreds of thousands of fraudulent (FAKE) ballots” and a news conference advancing similar claims. Barr, meanwhile, was spotted at the White House, though an official said that was for a meeting with White House Chief of Staff Mark Meadows, not Trump.

An administration official, like others speaking on the condition of anonymity to detail a sensitive topic, told The Post that in recent months, Barr and Trump have “barely spoken” though they did have a conversation the week before Thanksgiving. The official said Barr has clashed with the president or his advisers recently.

Before the election, the president was frustrated that John Durham, the U.S. attorney specially tapped by Barr to investigate the FBI’s 2016 investigation of Trump’s campaign, was not producing results that might publicly discredit his political opponents and aid his reelection bid. Then, Trump was upset the Justice Department was not doing more to support his claims of massive fraud, the official said.

Trump had made his displeasure known publicly. In October, after it was reported that Durham would not release a report before the election, Trump said the delay was “a disgrace” and said he would relay his thoughts directly to Barr.

“If that’s the case, I’m very disappointed,” Trump said during an interview with radio host Rush Limbaugh. “I think it’s a terrible thing. And I’ll say it to his face.”

This past weekend, Trump took aim at the Justice Department and the FBI over their failure to back his election fraud claims.

“You would think if you’re in the FBI or Department of Justice, this is the biggest thing you could be looking at,” Trump said on the show Sunday Morning Futures. “Where are they? I’ve not seen anything.”

The president also suggested the bureau and the Justice Department were possibly “involved,” though did not offer any clarity.

Administration officials said those public disputes have also played out in private, as Trump has been annoyed that Barr did not come out publicly in recent months to support the president or take more forceful action to investigate fraud. He has complained to advisers about his attorney general, two officials said, and the frustration has filtered to Barr even as the men talk less frequently than they once did.

The president has also been annoyed that Barr has expressed support for FBI Director Christopher A. Wray, whose public statements contradicting Trump — about election security and domestic extremism — made him a frequent target of the president’s rage, an administration official said.

“There have been clashes,” the official said.

In the interview with the Associated Press, Barr endeavored to make clear that whatever disputes Trump might have with the election, the Justice Department would not be the appropriate institution to resolve them. The Justice Department, he said, examines crimes, while state or local officials audit voting results.

“There’s a growing tendency to use the criminal justice system as sort of a default fix-all, and people don’t like something they want the Department of Justice to come in and ‘investigate,’ ” Barr told the Associated Press.

Barr did on Tuesday take a step that might appease Trump and his allies, revealing that, in an order signed on Oct. 19 and kept secret until now, he had appointed Durham as special counsel examining how the FBI investigated the Trump campaign in 2016 and beyond.

“Following consultation with Mr. Durham, I have determined that, in light of extraordinary circumstances relating to these matters, the public interest warrants Mr. Durham continuing this investigation pursuant to the powers and independence afforded by the Special Counsel regulations,” Barr wrote in the order.

As special counsel, Durham is authorized to investigate “whether any federal official, employee, or any other person or entity violated the law in connection with the intelligence, counter-intelligence, or law-enforcement activities directed at the 2016 presidential campaigns, individuals associated with those campaigns, and individuals associated with the administration of President Donald J. Trump, including but not limited to Crossfire Hurricane and the investigation of Special Counsel Robert S. Mueller III.”

Crossfire Hurricane is the name FBI agents gave to their investigation of Trump campaign associates who they suspected might be involved with Russian election interference. Mueller took over that probe after Trump fired Wray’s predecessor, James B. Comey.

In a letter to lawmakers Tuesday explaining his decision, Barr said that although he had expected Durham to finish his work by the summer, delays created by the coronavirus pandemic and the discovery of additional information pushed back that timeline.

“In advance of the presidential election, I decided to appoint Mr. Durham as a Special Counsel to provide him and his team with the assurance that they could complete their work, without regard to the outcome of the election.”

The letter states that Barr waited to make that decision public until after the election, though it does not indicate why he waited until December to do so.