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."
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.
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.