WASHINGTON (Reuters) - By picking fellow Republican South Carolina Governor Nikki Haley to serve as U.S. ambassador to the United Nations, U.S. President-elect Donald Trump's pick rounded out his early Cabinet choices with his first woman and ethnic minority.

But he also opted for a state politician with little experience in the federal government or international diplomacy who has been a sharp critic, backing two of his rivals and criticizing the harsh rhetoric of the presidential campaign.

In tapping the popular governor of a state that supported him, Trump's choice could signal an attempt to reach out to minorities in the wake of his Nov. 8 victory following a bitterly divisive campaign.

His victory has sparked protests and concerns by those worried that his denunciation of immigrants, Muslims and Hispanics during the campaign could translate into policies eroding civil rights.

Trump said on Wednesday that Haley could bring people together and was "a proven dealmaker" who "will be a great leader representing us on the world stage."

Haley, 44, represents what some Republicans have said could be the new face of the Republican Party: a younger, more diverse generation of leaders who could help bolster conservatives as U.S. demographics shift.

The daughter of Indian immigrants, she drew national attention in 2015 when she led a push to remove the Confederate battle flag from the state capitol grounds in Columbia after a white gunman killed nine people at a historic predominantly African-American church in Charleston.

But Haley, now serving her second four-year term as governor, has little experience in foreign policy and the diplomatic issues likely to come before the United Nations.

In a statement on Wednesday, she praised the state's residents for taking "a chance on a little-known, 38-year old, minority, female governor" when she took office six years ago.

ANOTHER OUTSIDER

Like Trump, Haley came to politics as an outsider.

After years working in her family's gift shop in Bamberg, a small town an hour south of the state capital, she ran for state representative in 2004 and defeated a nearly 30-year incumbent, touting her fiscal conservatism while brushing off racial slurs.

She won her gubernatorial bid in 2010 on a platform of reform, receiving the endorsement of former Alaska Governor Sarah Palin, a former Republican vice presidential nominee and darling of the party's Tea Party wing.

Still, Haley has not hesitated to call out fellow Republicans, including Trump. In January, she offered the party's rebuttal to President Barack Obama's State of the Union address, seizing the spotlight in what was seen as a strong rebuke of Trump.

Haley called for tolerance and civility in her remarks. Although she never mentioned Trump by name, she urged Americans not to "follow the siren call of the angriest voices," adding: "No one who is willing to work hard, abide by our laws, and love our traditions should ever feel unwelcome in this country."

But she told the Federalist Society recently that although she was not an early or vocal supporter of Trump, she did vote for him and was "thrilled" that he won.

Born to Sikh parents who emigrated to South Carolina from India, she is no stranger to U.S. racial and ethnic tensions.

While Trump won with the lowest minority vote in decades,, Haley has scolded Republicans for not working harder to broaden their appeal beyond white Americans.

"Our approach often appears cold and unwelcoming to minorities. That's shameful and that has to change," she said in a 2015 National Press Club speech. "It’s on us to communicate our positions in ways that wipe away the clutter of prejudices."

Although she worked to heal the racial tensions that exploded after the gun attack at the Emanuel African Methodist Episcopal Church in 2015, she has also been critical of the Black Lives Matter movement that gained ground after a series of high-profile shootings of unarmed African-Americans by police.

"Some people think you have to yell and scream in order to make a difference. Well, that's just not true," she told the National Press Club. "When the sound is quieter, you can actually hear what someone else is saying and that can make a world of difference."

TRIPS ABROAD

On Wednesday, Haley said, "When the President believes you have a major contribution to make to the welfare of our nation, and to our nation’s standing in the world, that is a calling that is important to heed."

Her international experience is largely centered on her efforts to draw foreign businesses to South Carolina, including at least eight overseas trips, local media reported.

One - a June 2011 trip billed as an economic development mission to Europe and the Paris Air Show - cost the state $158,000 and drew criticism back home over its luxury accommodations and a hotel party.

She said afterwards she did not know how much was spent and had learned a lesson, even as she pledged to keep up the sales pitches, the Charleston Post and Courier reported at the time.

"There is a method to the madness," she said, according to the newspaper. "I am selling the state the only way I know how."

The Post and Courier said her trips included trade show visits and economic development meetings, including stops related to BMW <BMWG.DE> and Volvo <VOLVb.ST>, two automakers with facilities in South Carolina. She has visited Germany, Sweden, Britain, Japan, Canada and India, it reported.

As governor, she has also been embroiled in the thorny issue of nuclear waste amid federal facilities in the state aimed at storing and converting such materials.

Earlier this year, she fought to have some nuclear material from Japan headed for South Carolina moved to New Mexico.

"Critics will ask if Nikki Haley has been engaged in int'l affairs. I've had convos w/her on & off over the years. She has a strong worldview," Dan Senor, a former adviser to 2012 Republican Presidential nominee Mitt Romney, said on Twitter.

(Writing by Susan Heavey; Editing by Jonathan Oatis)