President Donald Trump wanted to fire special counsel Robert S. Mueller III in June, but dropped his demand when the White House’s top lawyer, Donald McGahn, threatened to resign when asked to relay the order to Justice Department leaders, The New York Times reported Thursday.

According to the newspaper, Trump at the time questioned if Mueller had conflicts of interest that should lead to his termination. That reportedly followed a wave of news reports that Mueller was looking into whether the president’s actions in response to the probe into Russia’s 2016 election meddling and potential ties between the Trump-Pence campaign and the Kremlin had obstructed justice.

Trump alleged that Mueller resigned his membership at the Trump National Golf Club in Sterling, Virginia, after a spat over fees, the Times reported. The president also alleged that the former FBI director is unable to be objective in the DOJ investigation because he had once worked for a law firm that had represented Jared Kushner, Trump’s son-in-law, who also worked on the campaign and is now a senior White House adviser.

According to the report, Trump also contended that Mueller might be out for payback after interviewing for another term as FBI chief only to be passed over.

White House Press Secretary Sarah Huckabee Sanders and her top deputy, Raj Shah, are in Switzerland for the World Economic Forum with Trump, six hours ahead of Washington time. Neither has responded to a request for comment. White House lawyer Ty Cobb, as well as deputy press secretaries Hogan Gidley and Lindsay Walters, are in Washington. They have also not responded to a request for comment.

The report marks the first time the president is alleged to have tried to fire Mueller. The Times also reported that Mueller knows about the firing demand, and it comes as the special counsel is negotiating with the president’s personal lawyers about a potential Mueller-Trump interview as part of the investigation.

The Times cited four sources in its report.

Watch: Lessons for 44 Years of Special Investigations

The news broke 24 hours after Trump, during an impromptu press conference with reporters in the West Wing office of Chief of Staff John F. Kelly, said he would talk to Mueller — and do so under oath.

Trump told reporters Wednesday evening he is “disturbed” by allegations of internal FBI opposition to his presidency. He also would not say he has confidence that Mueller will treat him fairly.

“I would love to do it, and I would like to do it as soon as possible,” Trump said. “I would do it under oath, absolutely.”

The president indicated his meeting with the special counsel could happen within three weeks, but added it would be “subject to my lawyers.”.

In a remarkable back-and-forth that lasted about 14 minutes when the president popped into a meeting on immigration between Kelly and reporters, Trump also insisted he is being investigated for obstruction of justice by Mueller because he “fought back” against claims that his presidential campaign colluded with Russians.

“You fight back, oh, it’s obstruction,” Trump said.

Trump attacked the length of the DOJ probe, saying it has gone on too long. He lightly questioned its validity, citing lost FBI mobile device text messages and slamming Deputy FBI Director Andrew McCabe over contributions his wife’s Virginia state Senate campaign got from Clinton ally Terry McAuliffe, a former commonwealth governor.

The alleged episode conjures up memories of former President Richard Nixon, who fired Justice Department officials during the Watergate scandal and eventually resigned. Trump joined a small group, including Nixon, when he fired FBI Director James B. Comey in May, allegedly in part over the Russia probe.

Even some prominent Republican lawmakers have said publicly that Trump should not fire Mueller, saying it would cross a legal line and raise serious questions about the future of his tenure.

Once Mueller wraps his investigation, he is not expected to try to indict Trump. That means his findings would be fodder for potential impeachment proceedings in the House. So far, House Republicans are standing firmly by the president — but things could change if Democrats win control of both chambers in November’s midterms.

“I’ve said it before, and I am saying it again: firing the special counsel is a red line that the president cannot cross,” Senate Intelligence Vice Chairman Mark Warner, a Virginia Democrat, said in a statement Thursday night. “Any attempt to remove the special counsel, pardon key witnesses, or otherwise interfere in the investigation, would be a gross abuse of power, and all members of Congress, from both parties, have a responsibility to our Constitution and to our country to make that clear immediately.”

Niels Lesniewski contributed to this report.