Nikki Haley, the sole Republican challenger to Donald Trump, dropped out of the US presidential race on Wednesday after the former president cruised to victory in the Super Tuesday primary elections.
“The time has now come to suspend my campaign,” Ms Haley said at an event in Charleston, South Carolina.
“I said I wanted Americans to have their voices heard. I have done that.”
The former US ambassador to the UN quit the race after it became clear from Tuesday's primaries that she had no realistic path to clinching the Republican nomination.
“I have no regrets. And although I will no longer be a candidate, I will not stop using my voice for the things I believe in,” she added.
Mr Trump has won every state to have held a primary so far, with the exception of Vermont, and has secured 995 delegates, compared to Ms Haley's 89, according to the Associated Press.
A total of 1,215 delegates are needed to secure the nomination.
“They call it Super Tuesday for a reason,” Mr Trump said at his Mar-a-Lago resort election night watch party.
“This is a big one. And they tell me, the pundits and otherwise, that there’s never been one like this.”
As Tuesday night's results painted a clearer picture of defeat for Ms Haley, her fellow Republicans moved quickly to intensify pressure on the former South Carolina governor to step aside.
Pro-Trump Senator Lindsey Graham, also representing Ms Haley's home state, told CNN: “It’s pretty clear that people have spoken. I voted for Trump, not against Nikki. And at the end of the day, there’s really no pathway left. The sooner we can come together, the better.”
Ms Haley's withdrawal from the race means that the November election will almost certainly be a re-run of the 2020 race, pitting Mr Trump against President Joe Biden.
The two rivals were already on track to secure the nominations of the Republican and Democrat parties.
While Ms Haley did not endorse Mr Trump, she did acknowledge he was likely to become the nominee.
“It is now up to Donald Trump to earn the votes of those in our party and beyond who did not support him,” she said.
“And I hope he does that. At its best, politics is about bringing people into your cause not turning them away. And our conservative cause badly needs more people. ”
Ms Haley leaves the 2024 presidential contest having made history as the first woman to win a Republican primary. She beat Mr Trump in the District of Columbia on Sunday and Vermont on Tuesday.
She had insisted she would stay in the race through Super Tuesday and crossed the country campaigning in states holding Republican contests.
Ultimately, she was unable to knock Mr Trump off his glide path to a third straight nomination.
