Nikki Haley, U.S. ambassador to the United Nations, has resigned, CBS News' Fin Gomez has confirmed, according to a senior administration source. 

President Trump has accepted her resignation, but he tweeted that a "big announcement" was coming at 10:30 a.m.

White House press secretary Sarah Sanders told pool reporters in a statement, "President Trump and Ambassador Nikki Haley will meet in the Oval Office at 10:30 a.m. this morning" in an event open to cameras and the press pool, meaning only a handful of journalists will be present.  

Axios first reported Haley's resignation.

Haley has charted her own course during the Trump administration, admitting in a recent op-ed that sometimes she disagrees with the president. Her op-ed was a response to an anonymous op-ed published in the New York Times from someone who identified as a senior administration official. Haley's op-ed was headlined, "When I challenge the president, I do it directly. My anonymous colleague should have, too."

"I, too, am a senior Trump administration official," Haley wrote in her op-ed. "I proudly serve in this administration, and I enthusiastically support most of its decisions and the direction it is taking the country. But I don't agree with the president on everything. When there is disagreement, there is a right way and a wrong way to address it. I pick up the phone and call him or meet with him in person."