President-elect Donald Trump has announced he will nominate a Republican critic who once rebuked him for failing to disavow white supremacists as US ambassador to the United Nations.

South Carolina Governor Nikki Haley, a daughter of Sikh immigrants from India with little previous foreign policy experience, is the first woman picked for Trump's cabinet, injecting a measure of diversity in a group that until now has consisted solely of white men.

"Governor Haley has a proven track record of bringing people together, regardless of background or party affiliation, to move critical policies forward for the betterment of her state and our country," Trump said in a statement.

"She is also a proven deal-maker, and we look to be making plenty of deals. She will be a great leader representing us on the world stage."

The 44-year-old politician has been governor of South Carolina since 2011 [Richard Shiro/AP]

Haley's nomination must be confirmed by the Senate.

"The United States faces enormous challenges here at home and internationally, and I am honoured that the president-elect has asked me to join his team," Haley said in a statement, accepting the offer.

The 44-year-old politician, who has been governor of South Carolina since 2011, is a rising star in the Republican Party's right wing.

Haley rose to prominence after the former vice presidential candidate Sarah Palin endorsed her in a Republican primary during her campaign for governor in 2010, part of an effort to tap female candidates from the extreme-right Tea Party movement.

She later won widespread praise for backing the removal of the Confederate flag from the South Carolina state house after the 2015 killings.

The flag, which Haley had previously supported, is associated with slavery and opposition to civil rights reform.

'Very, very weak'

Haley was fiercely critical of Trump during the campaign, calling him "everything a governor doesn't want in a president" in February.

She supported Senator Marco Rubio during the Republican primary race before endorsing Senator Ted Cruz.

"I will not stop until we fight a man that chooses not to disavow the KKK. That is not a part of our party. That is not who we are," Haley said.

She also denounced Trump's promise to ban Muslims from entering the United States as "un-American."

Trump called her "very, very weak" on immigration.

However, Haley said she voted for Trump in the election, describing him as "a friend and supporter before he ran for president."

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Source: AFP