Ms. Haley said she had been a “lucky girl” to have served in the government and said she was proud of her tenure. She singled out White House officials Jared Kushner and Ivanka Trump, the president’s son-in-law and daughter, for praise.
Ms. Haley was a frequent critic of Mr. Trump during the 2016 campaign and had endorsed two of his primary opponents, Sens. Marco Rubio of Florida and Ted Cruz of Texas.
She clashed with the White House last spring after saying the Trump administration would imminently impose new sanctions against Russia over its support for the regime of President Bashar al-Assad in Syria. When White House officials later said she spoke prematurely, she issued a sharp retort: “With all due respect, I don’t get confused,” she said.
Her resignation sent shock waves through the diplomatic community at the U.N., where she was seen as a fierce advocate for Mr. Trump’s views. The news stunned diplomats and U.N. officials who said they didn’t see it coming.
U.N. officials said that Ms. Haley hadn’t informed Secretary-General António Guterres in advance of her decision to depart.
.. The ambassadorial post has sometimes been a springboard for U.S. ambassadors with higher ambitions.