Trump spoke as he met with Haley Tuesday morning in the Oval Office, calling her a "very special" person. He added that she told him six months ago that she might want to take some time off. Trump said that together they had "solved a lot of problems."
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VIDEO: President Trump meets with Nikki Haley regarding resignation
UN Ambassador Haley explains resignation
Haley was appointed to the U.N. post in November 2016.
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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.
MORE: Nikki Haley and other notable Trump resignations, firings
The Associated Press and ABC News contributed to this report.
DEVELOPING...We will add more details to this report as they become available.