Donald Trump is 25 days into his presidency and may already be preparing to use his trademark phrase "You're fired" on several prominent staff members.

Several high-profile administration staffers reportedly have their heads on the chopping block, and according to US media the most likely to get ousted first is National Security Advisor Mike Flynn .

Flynn is under increasing pressure to resign after it was revealed he had spoken to Russian officials about lifting sanctions before he was sworn in as a White House advisor.

Private citizens conducting foreign policy discussions with other countries' representatives is illegal.

Michael Flynn. (AP)

"The knives are out," one White House staffer told CNN .

"There's a lot of unhappiness about this."

And when asked on NBC if Flynn had Trump's confidence, senior policy advisor Stephen Miller refused to defend him.

"It's not for me to tell you what's in the president's mind," Miller said.

But despite the displeasure over Flynn, Trump may keep him around out of loyalty.

Flynn was a vocal supporter of Trump during the campaign, standing by the president during a series of scandals.

Trump owes no such loyalty to White House chief-of-staff Reince Priebus, who officially holds the most influential post outside the Oval Office.

Donald Trump and Reince Preibus at the former's presidential victory speech. (AP)

Priebus, the former chair of the Republican National Committee, has been blamed for the botched rollout of Trump's travel ban , a longtime friend of Trump said.

"(Trump) doesn't waste a lot of time," Christopher Ruddy said.

"If he thinks somebody is not performing, he moves pretty quickly."

Priebus himself has found himself sidelined by the increasingly influential Steve Bannon , the senior counsellor who has usurped him as Trump's chief advisor.

The White House typically has a high turnover of staff, with Barack Obama going through four chiefs-of-staff during his eight-year tenure.

But a staff shakeup less than a month into Donald Trump's presidency would be unprecedented.

The White House has denied it was interviewing a replacement for Sean Spicer , the press secretary whose three-week-old stint has been widely criticised.

Fox News contributor and former Navy SEAL Carl Higbie confirmed he spoke to the administration about a communications role, but has not yet been offered a job.

Trump was reportedly upset at Saturday Night Live for Melissa McCarthy 's depiction of Spicer.

A Trump donor told Politico that the president did not like Spicer being portrayed by a woman because he "doesn't like his people to look weak".

McClatchy DC also reports Trump is looking to cut back on staff in the First Lady's office, which still has many roles unfilled.

Donald Trump and his wife Melania at the New Year's Eve celebration at Mar-a-Lago, Florida. (AP)