Former Fox News commentator KT MacFarland has been kicked out of her role as deputy national security adviser by her newly appointed boss Lt General HR McMaster.

She is the third close Trump ally to be removed from the National Security Council after Steve Bannon was ousted on Wednesday and McMaster's predecessor, Lt Gen Michael Flynn, resigned in February.

McFarland, 65, will now become the US ambassador to Singapore, an insider told Bloomberg.

Heading out: Ex-Fox News commentator and close Trump ally TK MacFarland will be dropped as deputy national security adviser in the coming weeks, White House insiders claim

Shake up: Change is yet another shake up since Lt Gen Michael Flynn (left) quit in February. His replacement, Lt General HR McMaster (right), is restructuring the NSC

MacFarland took over the role on January 20, at the beginning of the Trump administration, and had told The Hill in February that despite Flynn's departure she was going nowhere.

'I just met with the president and he asked that I stay on. I'm thrilled to do so,' she said.

But in two weeks, the insider says, she will be moving on to the tiny but economically powerful city-state of Singapore.

The source spoke on condition of anonymity as they are not authorized to discuss personnel moves.

MacFarland's ousting has been described as a promotion, according to USA Today, as Singapore is a noted ally of the US. The paperwork is still being written up.

McFarlane's now-former colleague, deputy national security adviser Dina Powell - a former Goldman Sachs executive - will remain in the position, the source said.

This is the latest in a string of shake-ups within the White House, just four months into Trump's presidency.

They come as his administration continues to deal with the fallout from claims that his aides were communicating with Russia.

Allies: MacFarland (second from left, in January) is expected to become Ambassador to Singapore. Her fellow deputy national security adviser, Dina Powell, will remain on staff

In January Flynn stepped down after it emerged that the had been involved in meetings with Russian officials prior to Trump taking over.

He claimed that 'inadvertently briefed the Vice President Elect and others with incomplete information' as he departed.

His replacement, McMaster, has been given carte blanche to remake the department as he sees fit.

That meant curtains for Bannon's time as a national security insider.

The right-wing media boss was dropped from the National Security Council on Wednesday, amid rumors that Jared Kushner had issued a series of leaks against him.

Dropped: MacFarland, Flynn and - as of Wednesday - Steve Bannon (pictured) have all been dropped from the NSC. Rumors abound that Bannon's position in the White House is shaky

It was reported Saturday that the pair had had a sit-down meeting to smooth their troubled relationship, at the demand of chief of staff Reince Priebus.

And although he remains an adviser to Trump, he's also been blamed for the failure of two of key proposals: Trump's Obamacare replacement and the travel ban, which he drafted.

That means he's liable to lose his job - as is Priebus, who is struggling to tamp down the incessant in-fighting - insiders told the Wall Street Journal on Saturday.

Ex-Goldman Sachs employee Gary Cohn, one of Trump's economic advisers and a supposed candidate for Priebus's job, denied the claims, telling the journal: 'Reince is leading our team effectively.'

In another change, McMaster has reduced the responsibility held by homeland security expert Tom Bossert.