By MATTHEW LEE, AP Diplomatic Writer

WASHINGTON (AP) — U.N. Ambassador Nikki Haley plans to resign, The Associated Press has learned.

President Donald Trump tweeted that he has a "big announcement with my friend Ambassador Nikki Haley in the Oval Office at 10:30 a.m."

Congressional and Trump administration officials told the AP that Haley plans to resign. They spoke on condition of anonymity because they weren't authorized to speak on the record ahead of Trump's announcement. They did not provide a reason.

Haley was appointed to the U.N. post in November 2016.

Before she was named by Trump to her U.N. post, Haley was governor of South Carolina, the first woman to hold the post. She was re-elected in 2014.

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