US President Donald Trump has accepted the resignation of his UN ambassador Nikki Haley, according to US media reports.
Ms Haley would not confirm the reports when asked by the Reuters news agency at the White House on Tuesday.
Mr Trump has tweeted that a “big announcement” is due with his “friend” at 10:30am local time (3.30pm BST).
Big announcement with my friend Ambassador Nikki Haley in the Oval Office at 10:30am.
— Donald J. Trump (@realDonaldTrump) October 9, 2018
Congressional and Trump administration officials have told the Associated Press that Ms Haley plans to resign.
They are said to have spoken on condition of anonymity because they weren’t authorised to speak on the record.
Ms Haley was appointed to the UN post in November 2016.
She had previously been the governor of South Carolina, and was the first woman to hold the post.
Ms Haley was re-elected in 2014.