Indian-American former presidential hopeful Nikki Haley has said that she will vote for her ex-opponent and boss Donald Trump in the November US election, breaking her silence on the matter since exiting the Republican presidential primary more than two months ago.

Haley, 52, however, stopped short of an official endorsement.

Haley, who once served as Trump's United Nations ambassador, was the last of his major rivals to drop out of the party primary contest, in early March.

“I will be voting for Trump,” Haley said on Wednesday in response to a question during her appearance at the Hudson Institute, a top conservative think-tank in the American Capital, as she delivered a speech on national security and foreign policy.

“As a voter, I put my priorities on a president who's going to have the backs of our allies and hold our enemies to account, who would secure the border, no more excuses; a president who would support capitalism and freedom; a president who understands we need less debt, not more debt,” she said.

“Trump has not been perfect on these policies. I've made that clear many, many times. But (Joe) Biden has been a catastrophe. So, I will be voting for Trump. Having said that... I stand by what I said in my suspension speech," she said.

Haley was born Nimarata Nikki Randhawa in Bamberg, South Carolina, to immigrant Sikh parents from Amritsar, Punjab. Haley is the first Indian-American to serve in a presidential cabinet.

Haley said she has “no regrets” about her Republican primary bid: “We left it all on the field.” She also thanked the primary voters who have continued to back her even after she withdrew from the race — a potential warning sign for Trump. And she reiterated the call she’d made when exiting the race in March for the former president to reach out to those voters.

"Trump would be smart to reach out to the millions of people who voted for me and continue to support me and not assume that they're just going to be with him. I genuinely hope he does that,” Haley said in response to the question.

Anti-Trump Republican voters largely coalesced behind Ms Haley's presidential bid earlier this year and her dormant candidacy is still picking up support more than two months after she left the race.

She won more than 20 per cent of the vote in at least two state primary elections over the past fortnight.

But she did not call on her supporters to do the same.

"I stand by what I said in my suspension speech," she told the audience.

Speculation is now likely to grow over whether Haley will formally mend ties with Trump and endorse him.

In her speech, the former South Carolina governor slammed President Biden on his foreign policy and let China, Russia, and Iran grow stronger.

“Since the fall of Afghanistan, North Korea has gotten more aggressive towards South Korea and Japan. China is preparing to invade Taiwan. Of course, Iran and Russia have already started wars of their own. Without the Afghanistan debacle, Iran would have thought twice before letting Hamas attack Israel. For that matter, Russia likely would not have invaded Ukraine,” she said.

“While the Ukrainians have proven to be amazing fighters, Biden refuses to help them win. He gives them just enough to survive while Russian missiles and tanks grind their country to dust. It seems like the President wants a negotiated ceasefire in which Ukraine cedes some of its territory that Russia stole. That will only leave Russia as the winner and wanting more,” she alleged.

The same goes for Israel, she said.

Hamas was better positioned to attack Israel because Biden spent three-plus years appeasing Iran. He eased sanctions, forked over billions of dollars, and begged the Ayatollahs to get back in the nuclear deal, she said.

“Biden has given Iran nothing but cash and time. Cash and time it used to strengthen its terrorist proxies. Cash and time are used to get to the brink of a nuclear bomb. Joe Biden's legacy is already clear. He will go down in history as the commander-in-chief who refused to stop our enemies. He will be remembered for spending more on national debt interest than national defence. He weakened America while letting China, Russia, and Iran grow stronger,” Haley said.

Biden campaign officials said Haley’s remarks would not sway the anti-Trump moderates and independents who reject the violence and division that Trump represents.

“Nothing has changed for the millions of Republican voters who continue to cast their ballots against Donald Trump in the primaries and care deeply about the future of our democracy,” Michael Tyler, the communications director for Biden’s re-election campaign, said in a statement.

“Only one candidate shares those values, and only one campaign is working hard every day to earn their support — and that’s President Biden’s.” The Biden campaign has been working behind the scenes to reach out to high-profile Republicans and Haley voters. It is also planning to roll out a grass-roots group with dedicated staff workers to organise Republican voters in key battlegrounds.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.