"Ivanka has been just a great friend and they do a lot of things behind the scenes that I wish more people knew about".
Trump, making the announcement at the White House, told reporters that Haley had informed him about six months ago that at the end of a two-year period on the job, she'd want to take a break.
Trump and Haley confirmed Tuesday in the Oval Office that the president had accepted her resignation.
Responding to media speculation, she insisted that she was not planning to run for president against Trump in 2020, when she might be seen as a more moderate Republican alternative.
She thanked Trump for giving her the "honor of a lifetime" to "serve a country I love so very much".
Haley cited Trump's tough trade policy, his decision to leave the Iran nuclear deal and move the U.S. Embassy in Israel to Jerusalem, which infuriated many allies and regional partners.
"She's made it a very glamorous position", Mr Trump said. According to Ms Haley's Twitter account, the two just spent the weekend together in SC. "If I disagree with something and believe it is important enough to raise with the president, I do it", she wrote at the time. She would campaign for Trump, she added.
In the past year, the two-term governor from SC has emerged as a close confident of Trump and was strongly pushing for Trump's foreign policy agenda at the United Nations, attracting frequent praise from Trump himself. Trump unceremoniously announced his firing of former secretary of state Rex Tillerson in March in a tweet.
Haley is merely the latest in a long line of Cabinet officials or senior administration officials to exit. Haley discussed resigning with the president last week.
Grenell spent eight years serving as a USA spokesman and political appointee to the United Nations under the George W. Bush administration - making him the longest-serving U.N. appointee in history. "I think CNN would support her".
Haley was appointed to the United Nations post in November 2016.
When asked if she would take the job by then-chief of staff Reince Priebus, Haley was intrigued but had some conditions.
"She got to know the players, she got to know China, Russia, and India.they like her...they respect her".