WASHINGTON, Jan. 26 (Xinhua) -- U.S. President Donald Trump had intended to fire special counsel for the Russia investigation Robert Mueller last June but backed down, local media reported Thursday, citing sources familiar with the matter.

Trump's order did not go through because White House counsel Don McGahn threatened to quit if the president insisted on doing it, according to a report from the New York Times.

The report said Trump expressed concern over three possible conflicts of interest, including Mueller's one-time membership at the Trump National Golf Club, his connection with a law firm that represented Trump's son-in-law and the interview Mueller had with the president for the job as head of the FBI.

"We decline to comment out of respect for the Office of the Special Counsel and its process," White House lawyer Ty Cobb said in a statement to CNN.

Mueller is investigating allegations of Russian interference in the 2016 U.S. presidential election and possible collusion between the Trump campaign and Moscow.

Last May, Mueller, who had spent 12 years as director of the FBI, was appointed special counsel to oversee the Russia investigation.

The special counsel's team is also reportedly looking into any attempts by Trump to obstruct the investigation.

In response to the report, Democratic Senator Mark Warner, vice chairman of the Senate Intelligence Committee, tweeted that "firing the Special Counsel is a red line that the President cannot cross."

"Any attempt to remove the Special Counsel, pardon key witnesses, or otherwise interference in the investigation, would be a gross abuse of power," he said.

Trump has repeatedly denied allegations of collusion between his campaign and Russia while describing the Russia probe as a "hoax" or a "witch hunt."

Trump said late last year that he was not considering firing the special counsel, but speculation over the possibility has increased as investigators appeared to have gotten closer to Trump's inner circle.

The Justice Department confirmed Tuesday that Attorney General Jeff Sessions was interviewed for several hours last week by the special counsel's office.

The Sessions-Mueller interview was the first time that the Mueller team is known to have questioned a Trump cabinet member.

Former FBI Director James Comey was also reportedly questioned by the special counsel.

On Wednesday, Trump told reporters that he looks forward to speaking with Mueller as part of the ongoing Russia probe.

"I'm looking forward to it," Trump said at the White House. "I would do it under oath."

The president also said that he expected his interview with Mueller to happen in two or three weeks, and that whether he would show up was subject to his lawyers' advice. "But I'd love to do it," he said.

"There has been no collusion whatsoever," Trump said as he repeatedly did, adding "there's no obstruction whatsoever."