WASHINGTON : Donald Trump said Wednesday that White House counsel Don McGahn would soon be leaving his post, as Special Counsel Robert Mueller - who is leading the Russia election interference probe - closes in on the US president’s inner circle.

“White House Counsel Don McGahn will be leaving his position in the fall, shortly after the confirmation (hopefully) of Judge Brett Kavanaugh to the United States Supreme Court,” Trump announced on Twitter.

“I have worked with Don for a long time and truly appreciate his service!” he added, without offering any reason for McGahn’s departure.

Earlier this month, The New York Times reported that McGahn had “cooperated extensively” with Mueller’s team, taking part in at least three interviews with investigators totaling 30 hours. Trump, who has repeatedly called the probe a “rigged witch hunt,” said he had authorized his team to “fully cooperate” with investigators and provided hundreds of thousands of pages of documents.

But speculation quickly mounted about what McGahn might have specifically said about whether the Republican leader sought to obstruct justice.

The Times reported that McGahn had provided “detailed accounts” about episodes relating to alleged obstruction, citing a dozen current and former officials and other sources.

The information he provided included details about the president’s attempts to fire the special counsel, and Trump’s comments and actions during his firing of FBI director James Comey, according to the Times.

The newspaper said it was unclear whether Trump knew the extent of McGahn’s cooperation, noting that it is rare for a lawyer to be so open with investigators.

McGahn is a former commissioner and chairman of the Federal Election Commission. Before taking the White House post, he was working as a partner at the Jones Day law firm in Washington on issues of political law.

Trump suffered a one-two punch in court this month, when his longtime personal lawyer Michael Cohen pleaded guilty to campaign finance violations and former campaign manager Paul Manafort was found guilty of tax and bank fraud.

Senator Chuck Grassley, the chairman of the powerful Judiciary Committee, sent a cryptic tweet to Trump: “I hope it’s not true McGahn is leaving White House Counsel. U can’t let that happen.”