U.S. Ambassador to the United Nations Nikki Haley visited South Sudan and delivered a "harsh message" to the nation's President Salva Kiir. (Reuters)

President Trump had a message — more like an ultimatum — for the leader of this flailing, violence-torn African nation, a man who largely owes his position and the very existence of his country to the United States.

But he didn’t turn to the ostensible top U.S. diplomat, Secretary of State Rex Tillerson, to deliver the message. Instead, the messenger was Nikki Haley.

“I basically said the United States had invested well over $11 billion in South Sudan and into him and that we were now questioning that investment,” Haley, the tough-talking U.N. ambassador, said last week about her one-on-one discussion with South Sudanese President Salva Kiir.

Her diplomatic mission to Africa — which included visits to desperate refu­gee camps that more than once brought Haley to tears — illustrated in stark terms her trusted position and unusually direct relationship with the president. Trump routinely talks with her about matters of world affairs even as policy differences over Iran, Afghanistan and other issues have tested his relationship with Tillerson.

Haley said she will give a briefing to Trump and Vice President Pence early next week. She and Trump tried to connect by phone during the trip but were unable to do so because of poor cellular phone service, a spokeswoman for Haley said. She said she would provide Tillerson an in-person readout of her trip if schedules allowed.

U.N. ambassador Nikki Haley meets South Sudanese refugee children at the Nguenyyiel refugee camp in Gambella Region, Ethiopia October 24, 2017. (Tiksa Negeri/Reuters)

“I think that I’ll give options, and if asked I‘ll give the recommendation” about next moves for U.S. policy in the three sub-Saharan nations she visited, Haley said. And she expects to be asked. “Usually the president’s very good at that,” she said.

Haley’s prominent role in the Trump’s administration as a kind of shadow secretary of state has led to widespread speculation that the former South Carolina governor, who has no prior experience in foreign policy, could be in line to replace Tillerson — a job she insisted she does not want during a joint interview with The Washington Post and Reuters. Her rise has also put her on many Republicans’ shortlist as a potential presidential or vice-presidential candidate.

Haley denies any immediate ambitions, even as she does not hide her political instincts.

“I cannot even imagine it,” she said at the idea of running for the White House.

In explaining her new diplomatic role, Haley regularly invokes her statehouse experience in Columbia, S.C., saying the haggling and strategizing of electoral politics made her a better negotiator. Haley’s former pollster is a top adviser and accompanied her to Africa.

“When you’re a governor you’re very results-oriented and you’re always looking at what that final level needs to be. When I look at this administration, the results are there, “ Haley said early in the trip. “People may not like the way he gets to the results, which I think is really, it’s more of a communication thing.”

U.N. Ambassador Nikki Haley visited a U.N. aid camp in Juba, South Sudan Oct. 25. This anti-government protest caused her to cut the visit short. (The Washington Post)

Haley was late to support Trump and backed Sen. Marco Rubio (Fla.) in the Republican primary. But as part of his administration, Haley frequently serves as Trump’s chief messenger and interpreter on foreign policy.

She used a September address to the conservative American Enterprise Institute to telegraph the strategy Trump adopted a month later in refusing to endorse the U.N.-backed international nuclear deal with Iran. She used another address to the conservative Heritage Foundation this month to cheer the president’s decision as prudent and Reaganesque. Tillerson and other top Trump national security aides had argued against undermining a deal they see as flawed but valuable.

As Trump does, Haley also cites economic markers such as a soaring stock market as evidence of achievement and highlights national security successes in combating the Islamic State.

“If you take out the personality, take out the person, look at the results and you can’t deny it, you can’t deny it,” she said in Addis Ababa, Ethi­o­pia, the first stop in Africa last week.

At the end of the trip, Haley tweeted a picture of her caressing a young child and wrote: “With no education, abducted as child soldiers, young girls raped . . . We can’t take our eyes off the children of S. Sudan & DRC. #FutureLeaders.”

Tillerson, who was also traveling on a diplomatic mission last week, does not use Twitter. Neither he nor Haley does much to mask a sometimes chilly relationship, although both say they work in tandem.

Haley has broad license to speak on Trump’s behalf at the United Nations, which has occasionally led to grumbling from Tillerson’s allies and others, saying that she strays from her lane.

She said she is not bound to a strict set of talking points dictated from Washington, whether in her discussions with other U.N. diplomats or on the road.

“It goes back to the original conversation we had when he asked me to do this, it really does, because I didn’t want to leave being governor to go recite talking points,” Haley said of Trump.

“I can think for myself, I can do for myself. I am very aware of who I work for and very aware of the national security team, and I’m very aware of doing everything in the best interests of the United States and for peace and security around the world, and I’m very careful with how I use that flexibility,” she said.

“And credit goes to the president,” she continued. “When I go, he says, ‘Go do.’ I don’t go and go off the reserve or anything like that.”

The deaths of four American soldiers in an ambush in Niger earlier in October lent an immediacy to Haley’s larger goal of highlighting what she calls the risk of terrorists, some displaced from the Middle East, finding a new foothold in Africa.

She met with the leaders of each nation she visited — Ethiopia, South Sudan and Congo — and insisted that reporters traveling with her could see at least part of each meeting. In Ethiopia, that meant intervening with security agents attempting to keep the U.S. news media at bay.

That each of the strongmen agreed to receive her suggests that they knew she was Trump’s direct envoy, no matter her title. And what the leaders heard was a channeling and repackaging of Trump.

Her public warnings about the limits of U.S. patience, funding and diplomatic support were an unmistakable, if softer, reference to Trump’s “America First” message. And her impassioned pledges to help people displaced by war gave an empathetic face to a Trump foreign policy marked by suspicion of U.S. engagement abroad.

With Kiir, Haley said she brought along photographs of suffering refugees she had visited the day before at an Ethiopian camp where she heard harrowing personal stories of rape and murder. Kiir did not deny the atrocities attributed to his soldiers, she said.

“These are firm, candid conversations for a reason,” Haley said in the Post interview Friday in Kinshasa, Congo, her last stop in Africa.

“We don’t care about what they say and how pretty they say it,” Haley said of her talks with African leaders. “We care about what they do and how effective it is.”

That balance-sheet message is a familiar one for Haley, who has tried with some success to shake up moribund U.N. institutions and demand greater accountability. She frequently dangles the threat of cutbacks in U.S. funding, as Trump also did during his address to the U.N. General Assembly last month.

If the tense sessions in guarded government compounds were the meat of her trip, Haley’s three visits to refugee and civilian protection camps were the emotional heart. She toured huts, schools, a haven for traumatized women, another for traumatized former child soldiers and a women-run bakery. She hugged rape survivors and delivered polio vaccines. She asked grinning kids how old they were and was startled to learn that they did not reliably know the answer.

In one of the camps, Haley walked past signs proclaiming Trump a peacemaker and protector. In another, signs implored Haley to take messages of heartbreak and political frustration home to Washington.

If she saw those messages, Haley gave no sign. But the sight of aimless children milling in the U.N.-assisted camps brought Haley to tears.

Each camp housed desperate people who say they cannot go home. Living in the camps can mean children are schooled irregularly or not at all. Their parents have little opportunity to work, and the children’s chances may be no better.

Haley noted that those bleak prospects may also make these uprooted children susceptible to extremist ideology. And in that, she closed the loop between an impulse to help for the sake of helping and the Trumpian mandate to keep U.S. interests paramount.

“Those kids will be 18 one day. They’ll be an adult. And they’ll be an uneducated adult with no social skills that will have resented the fact that they were put in that situation,” Haley said. “And that’s dangerous for the United States, and that’s dangerous for the world.”