Nikki Haley, a former South Carolina governor and United Nations ambassador, has announced she is a candidate to become US president in 2024.

"Now is not the time to hold back. Now is the time for a strong and proud America," she tweeted, linking to a campaign video.

She is the second major Republican candidate to run - her ex-boss, Donald Trump, launched his bid in November.

Ms Haley is the third Indian American to seek a presidential nomination.

The former governor, 51, said in 2021 that she wouldn't challenge Mr Trump for the White House. But she changed her position in recent months, citing the need for "generational change".

Other Republicans who are tipped to launch their own White House campaigns include Florida Governor Ron DeSantis and former Vice-President Mike Pence.

Ms Haley has previously criticised Mr Trump's behaviour up to and during the 6 January 2021 attack on the US Capitol by his supporters.

The day after the riot, she said in a speech that "his actions since election day will be judged harshly by history".

Most early polls show Mr Trump with a comfortable lead in South Carolina, whose primary he won on his way to the presidency in 2016 - an indication of the uphill battle the former ambassador will have, even on what should be friendly ground.

A recent survey by the polling firm Trafalgar Group that included current and likely candidates has Mr Trump in first place with 43% and Ms Haley in fourth at 12%.

But another opinion poll released on Tuesday suggested Mr Trump's once-resilient political strength could be softening among members of his party.

Forty per cent of registered Republicans said he should not run for the White House in 2024, according to the Reuters/Ipsos survey, even as he remained the favourite among the party's field of potential candidates.

The same poll found that 52% of registered Democrats do not support Mr Biden running for re-election.

Other Indian Americans to run before Ms Haley were Louisiana Governor Bobby Jindal, whose bid in 2015 never gained significant traction, and current Vice-President Kamala Harris, who sought the 2020 nomination. (BBC)

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