Image copyright Reuters

US President Donald Trump's hawkish deputy national security adviser, Sebastian Gorka, has left the White House, it has been confirmed.

The latest White House departure came a week after his ally, ultra-conservative White House chief strategist Steve Bannon, was dismissed.

It is unclear whether Mr Gorka was also sacked or quit of his own accord.

He was quoted as writing in a letter that some in the White House were seeking to undermine Mr Trump.

"[G]iven recent events, it is clear to me that forces that do not support the MAGA [Make America Great Again] promise are - for now - ascendant within the White House," he reportedly wrote in the letter, printed on conservative news site the Federalist.

"As a result, the best and most effective way I can support you, Mr. President, is from outside the People's House."

However, unnamed White House officials told US media he had been forced out. "Sebastian Gorka did not resign, but I can confirm he no longer works at the White House," a source told Reuters news agency.

An unnamed official was quoted by the New York Times as saying the president's chief of staff, John Kelly, had "telegraphed his lack of interest in keeping Mr. Gorka during internal discussions over the last week".

Who else left Trump's White House team?

Steve Bannon, chief strategist - 18 August

Anthony Scaramucci, communications director - 31 July

Reince Priebus, chief of staff - 28 July

Sean Spicer, press secretary - 21 July

Mike Dubke, communications director, 30 May

Michael Flynn, national security adviser - 14 February

This photo sums up White House turmoil

Mr Gorka worked for Mr Bannon before they both joined the Trump administration: He was national security editor at Mr Bannon's Breitbart news website, often writing about the threat posed by Islamist militants.

Mr Bannon, sacked after a review by chief of staff Kelly, likewise pledged to remain loyal to President Trump.

In the letter attributed to him, Mr Gorka tells the president: "Regrettably, outside of yourself, the individuals who most embodied and represented the policies that will 'Make America Great Again,' have been internally countered, systematically removed, or undermined in recent months.

"This was made patently obvious as I read the text of your speech on Afghanistan this week… The fact that those who drafted and approved the speech removed any mention of Radical Islam or radical Islamic terrorism proves that a crucial element of your presidential campaign has been lost."

On Monday, Mr Trump ruled out withdrawing US troops from the country.

A US citizen who was born in the UK to Hungarian parents, Mr Gorka studied political science in Budapest and is the author of a best-selling book, Defeating Jihad: The Winnable War.

Like President Trump himself, he rails against the mainstream media, accusing the BBC and others of spreading fake news.