She cited a belief in term limits for public officials as the reason for her decision, along with a desire to take a breather from government work after 14 years in public office.
"By accepting gifts of luxury private flights, Ambassador Haley seems to be falling in line with other Trump administration officials who are reaping personal benefits from their public positions", CREW Executive Director Noah Bookbinder said in a Monday statement.
Trump said Haley "has been very special to me, done an incredible job" and is a "fantastic person", and he revealed that she first informed him six months ago of her plan to resign "maybe at the end of the year". Congressional Republicans involved in foreign policy matters and some key USA allies did not get advance word from Haley or the White House. Haley told reporters she will be campaigning for the president in 2020, quashing speculation that she might chart her own political course challenging the president.
Haley has been the face of Trump's "America First" policy at the United Nations, steering the U.S. withdrawal from several UN programs and ardently defending his hard-line policies against Iran and North Korea over their nuclear programs.
Haley, 46, was appointed to the U.N. post in November 2016 and last month coordinated Trump's second trip to the United Nations, including his first time chairing the Security Council. "They know that if we say we're going to do something, we follow it through", she said.
With Haley sitting at his side, Trump told a crowd of reporters that she will be leaving at the end of the year, explaining that her job as ambassador allowed her to get to know numerous other global players and world leaders.
Last month Haley wrote an op-ed in The Washington Post discussing her policy disagreements but also her pride in working for Trump.
President Donald Trump tweeted that he has a "big announcement with my friend Ambassador Nikki Haley in the Oval Office at 10:30 a.m".
In a January 2016 response to then-President Barack Obama's State of the Union address, she warned against following "the siren call of the angriest voices", a clear rebuke of Trump. Trump tweeted that "The people of SC are embarrassed by Nikki Haley".
Lindsey Graham (R-S.C.) was replacing Trump's public enemy, Attorney General Jeff Sessions, and Haley, a former governor of SC, would run for his Senate seat, some people speculated. She was re-elected in 2014. Some even suggested Haley was running for president in 2020 with Trump's support.