Under fire for his handling of the coronavirus crisis, US President Donald Trump on Friday announced a significant staff overhaul, naming North Carolina politician Mark Meadows as his new chief of staff, and replacing Mick Mulvaney, who has been acting in the role for more than a year.

Trump announced the surprise staff reshuffle in a series of Friday night tweets, saying Mulvaney would become the US special envoy for Northern Ireland.

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"I have long known and worked with Mark, and the relationship is a very good one," he wrote, thanking Mulvaney - who never shook his "acting" title - "for having served the Administration so well".

The long-rumoured move makes Meadows, who announced he was not seeking re-election for his House seat, effectively Trump's fourth chief of staff since taking office in 2017.

In 2012, while seeking a seat in Congress, Meadows suggested that then-US President Barack Obama be sent "home to Kenya or wherever it is", wading into the dubious controversy that the 43rd president was not born in the United States.

At that time, businessman Trump was also involved in the controversy.

Meadows was also entangled in a sexual harassment scandal involving his former top assistant.

Trump's decision to appoint Meadows comes as his administration has faced criticism for its handling of the novel coronavirus outbreak.

Mulvaney had been leading the inter-agency response to the virus until Trump designated Vice President Mike Pence to lead the whole-of-government effort more than a week ago.

Mulvaney has been marginalised inside the White House for months, taking on an increasingly narrow role.

And Trump has been eyeing the change for months but wanted to wait until after impeachment, according to a person familiar with his thinking, who spoke on condition of anonymity because the person was not authorised to discuss it publicly.

Mulvaney's allies, however, had long brushed off rumblings off his imminent departure and had said as recently as last month that he planned to stay at least through the election in November.