LAS VEGAS (Reuters) - Victoria Coates, one of President Donald Trump’s longest-serving national security aides, is leaving the White House soon to become a senior adviser at the Energy Department, the White House said on Thursday.

FILE PHOTO: The White House is visible on a cold, overcast day, WASHINGTON, U.S. February 5, 2020. REUTERS/Leah Millis/File Photo

Coates has been at the Trump White House since he took office three years ago and has been a key player in the administration’s deliberations on Iran and the Middle East.

But she had battled rumors that she was the author of an opinion article by someone styling themselves as “Anonymous” expressing opposition to Trump’s agenda that ran in the New York Times on Sept. 5, 2018.

“The White House leadership rejects rumors that have circulated recently and does not put any stock in the suggestion that Victoria Coates is the author of (the November 2019 book) ‘A Warning’ or the related op-ed in the New York Times,” said a senior administration official, speaking on condition of anonymity.

“Dr. Coates’ transition to the Department of Energy has been in the works for several weeks and reflects the continued trust and confidence the administration places in her as she takes on this sensitive role at the Department of Energy, where she will continue working to implement the president’s agenda,” the official said.

A White House statement said the move would take effect on Monday.

“We are enthusiastic about adding Dr. Coates to DOE, where her expertise on the Middle East and national security policy will be helpful,” Energy Secretary Dan Brouillette said in a statement. “She will play an important role on our team.”

The move comes as Trump’s national security adviser, Robert O’Brien, retools the National Security Council apparatus that he inherited from John Bolton, who left under fire from Trump as national security adviser last September.

O’Brien has been reducing the number of staff at the council.

He said in a statement that Coates has played a valued role in implementing Trump’s Middle East policy.

“While I’m sad to lose an important member of our team, Victoria will be a big asset to Secretary Brouillette as he executes the president’s energy security policy priorities,” O’Brien said.

Trump, who is on a Western swing for his re-election campaign, told reporters on Tuesday that he had his suspicions as to who “Anonymous” is, but would not elaborate.

A successor to Coates was not announced.