President Trump’s ambassador to the United Nations, Nikki R. Haley, said on Tuesday she would resign at the end of the year, marking a high-profile departure of one of the few women in the president’s cabinet.
Ms. Haley, a former governor of South Carolina, had been an early and frequent critic of Mr. Trump, so when he named her the envoy to the world body weeks after his election in November 2016, the appointment was seen as an olive branch.
“It was a blessing to go into the U.N. with body armor every day and defend America,” Ms. Haley, seated next to Mr. Trump in the Oval Office, told reporters. “I’ll never truly step aside from fighting for our country. But I will tell you that I think it’s time.”
Being the United Nations ambassador, she said, “has been an honor of a lifetime.”
Mr. Trump said Ms. Haley had informed him roughly six months ago that she wanted to take a break after finishing two years with the administration. He said he hoped Ms. Haley would return in a different role, and would name her successor within the next two or three weeks.
“She’s done a fantastic job and we’ve done a fantastic job together,” Mr. Trump said. “We’re all happy for you in one way, but we hate to lose you.”
Ms. Haley, who has long been seen as a potential presidential candidate, said she had no intention of running for the presidency in 2020, as has been speculated. Instead, she said, she plans to campaign for Mr. Trump’s re-election.
“I think you have to be selfless enough to know when you step aside and allow someone else to do the job,” Ms. Haley said.
The daughter of immigrants from India, Ms. Haley favored free markets and global trade and earned international attention for speaking out against the Confederate battle flag in the aftermath of the 2015 massacre at a black church in Charleston. During Mr. Trump’s presidential campaign, she sharply criticized his demeanor and warned what it might mean for American diplomacy — even suggesting that his tendency to lash out at critics could cause a world war.
As ambassador, Ms. Haley was an outspoken and often forceful envoy — someone whom foreign diplomats looked to for guidance from an administration known for haphazard and inconsistent policy positions. She was quick to voice her own opinions on the big policy issues that are high on her agenda, like Iran and North Korea.
Ms. Haley acknowledged her policy disagreements with the president in an op-ed in the Washington Post last month when she criticized an anonymous senior administration official who penned an opinion piece in The New York Times, describing a chaotic administration in which many of the president’s aides disagreed with their boss.
“I don’t agree with the president on everything,” Ms. Haley wrote. “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.”
Ms. Haley also collided with the national security adviser, John R. Bolton, after she announced that Mr. Trump would lead a session of the United Nations Security Council devoted entirely to Iran. After European officials protested that this would showcase divisions in the West because of Mr. Trump’s decision to pull out of the Iran nuclear deal, the White House broadened the theme to countering weapons of mass destruction.
Mr. Bolton did not criticize Ms. Haley. But as a former ambassador to the United Nations, he drove the decision to shift the agenda. White House officials noted that under United Nations rules, Iran would have been entitled to send its president to the meeting — setting up the awkward possibility that Mr. Trump would have sat across a table from Iran’s leader.
Ms. Haley also has cast herself as someone able to sway her mercurial boss on issues like Russia sanctions, refugee resettlement and the value of the United Nations itself.
She was the first cabinet-level United Nations ambassador for a Republican administration since the end of the Cold War, and quickly made clear she saw the position as a steppingstone to a higher political office — a possibility that Mr. Trump may have resented.
She became a far more visible face of American foreign policy than her first boss at the State Department, former Secretary of State Rex W. Tillerson. Time magazine celebrated Ms. Haley’s ascendance by putting her on a cover as one of the women who are “changing the world.”
A March 9 article in Foreign Policy magazine, titled “Candidate Haley,” portrayed her as a “retail politician turning U.N. diplomacy into a ticket to the White House.”
“Nikki Haley has been a clear, consistent, and powerful voice for America’s interests and democratic principles on the world stage,” Speaker Paul D. Ryan, Republican of Wisconsin, said on Twitter. “She challenged friend and foe to be better.”
Earlier this year, Republicans close to the White House whispered about the possibility that Ms. Haley and Vice President Mike Pence run as a ticket together as early as 2020. However, Mr. Trump plans to run for re-election.
While Ms. Haley was among the few women in Mr. Trump’s cabinet, she is far from the first United States woman to hold the United Nations ambassador position. She succeeded Samantha Power and Susan E. Rice, who both worked for former President Barack Obama.
Other women envoys from the United States to the world body have included Madeleine Albright, Jeane Kirkpatrick, Anne Patterson, Rosemary DiCarlo and Michele Sison.
In a January 2016 response to Mr. Obama’s State of the Union address, she warned against following “the siren call of the angriest voices,” a clear rebuke of Mr. Trump.
And in December 2017, Ms. Haley said that women who had accused Mr. Trump of sexual misconduct “should be heard,” a surprising break from the administration’s longstanding assertion that the accusations were false and that voters rightly dismissed them when they elected Mr. Trump.
“They should be heard, and they should be dealt with,” Ms. Haley told CBS. “And I think we heard from them prior to the election. And I think any woman who has felt violated or felt mistreated in any way, they have every right to speak up.”
In August 2017, when Mr. Trump casually said at a televised news briefing that his administration could not rule out a “military option” to respond to the crisis in Venezuela, Ms. Haley was visibly dismayed.
On April 15, Ms. Haley announced that the administration would place sanctions on Russian companies found to be assisting Syria’s chemical weapons program — part of a menu of options to retaliate against a suspected gas attack that killed dozens on April 7.
But the next day, the White House announced that Mr. Trump had decided not to go forward with the sanctions, contradicting what Ms. Haley had said. The White House said she had gotten “ahead of the curve” and one official blamed Ms. Haley’s statement as “momentary confusion.” Ms. Haley testily responded that she did not “get confused.”
Compounding her political difficulties, that same weekend, the White House blocked a plan under which one of her advisers, Jon Lerner, would also advise Mr. Pence on national security policy, in a dual role.
The White House was angered by Mr. Lerner’s role in a “super PAC” that had supported one of Mr. Trump’s primary campaign opponents, Senator Marco Rubio of Florida, and by his involvement in the anti-tax Club for Growth, which had attacked Mr. Trump during his campaign for the Republican nomination for president.
Mark Landler and Eileen Sullivan contributed reporting.