High praise

Trump said Haley had told him six months ago that she was thinking of leaving by the end the year "to take a little time off." He was effusive in his praise of her.

"She has done an incredible job. She is a fantastic person, very importantly, but she also is somebody that gets it," Trump said on Tuesday. "She's done a fantastic job and we've done a fantastic job together."

Haley's name has come up as possible Republican running mate in the last two presidential elections and she could also become a US senator if fellow South Carolina Republican Lindsey Graham takes up a job in the Trump administration, as is often speculated.

Trump suggested the two of them jointly announce Haley's departure in the Oval Office, an administration official said, noting that Haley was the only outgoing senior member of Trump’s administration to be feted in this way.

Returning the favor, Haley praised Trump and his family for their support.

She described Jared Kushner, Trump's son-in-law and aide, as "such a hidden genius that no one understands" for his work on renegotiating the NAFTA trade deal and preparing a long-awaited Middle East peace plan that has not yet been released.

The feel-good nature of her resignation was markedly different from other high-profile departures from Trump's Cabinet. Trump unceremoniously announced his firing of former secretary of state Rex Tillerson in March in a tweet.

Haley was seen by her counterparts at the United Nations as a voice of clarity in a US administration that often gave off mixed signals on foreign policy, diplomats say.

"Nikki Haley is one of the most talented, most authentic US government officials that I have ever met," said UN ambassador for France, Francois Delattre.

But she has been overshadowed in recent months by the appointments of Trump loyalist Mike Pompeo as secretary of state and hawk John Bolton as White House national security adviser.

Pompeo has led policy on talks with DPRK, while Bolton has taken the lead on trying to implement Trump's hard line against Iran.

Reuters