President Donald Trump has not committed to a previous pledge to keep chief of staff John Kelly for the remainder of his term, part of widespread speculation about staffing changes that could soon sweep through his administration.

Mr Trump, in a wide-ranging interview that aired on Fox News Sunday, praised Mr Kelly’s work ethic and much of what he brings to the position but added: “There are certain things that I don’t like that he does.”

“There are a couple of things where it’s just not his strength. It’s not his fault. It’s not his strength,” said Mr Trump, who added that Mr Kelly himself might want to depart.

Asked whether he would keep Mr Kelly in his post through 2020, the president offered only that “it could happen”.

President Donald Trump walks across the South Lawn of the White House (Jacquelyn Martin/AP)

Mr Trump had earlier pledged publicly that Mr Kelly would remain through his first term in office, though many in the West Wing were sceptical.

Mr Trump said he was happy with his Cabinet but was thinking about changing “three or four or five positions”.

One of them is Homeland Security chief Kirstjen Nielsen, whose departure is now considered inevitable.

Mr Trump said in the interview that he could keep her on, but he made clear that he wished she would be tougher in implementing his hard-line immigration policies and enforcing border security.

White House Chief of Staff John Kelly looks on as President Donald Trump visits with Marines at the Marine Barracks Washington (Evan Vucci/AP)

Her eventual replacement will find there’s no getting around the immigration laws and court challenges that have thwarted the president’s hard-line agenda at every turn, even if there is better personal chemistry.

Mr Trump also discussed the removal of Mira Ricardel, a deputy national security adviser who is being moved to another position in the administration after clashes with the East Wing culminated in an extraordinary statement from first lady Melania Trump that called for her removal.

The president said Ms Ricardel was “not too diplomatic, but she’s talented” and downplayed the idea that his wife was calling the shots in the White House.

He also dismissed a series of reports that he had been fuming in the week after the Democrats captured the House of Representatives, claiming instead that the mood of the West Wing was “very light”.