HOOKSETT, United States, Jan 20, 2024 (BSS/AFP) - A US senator who sought this year's Republican presidential nomination endorsed Donald Trump on Friday in a boost to the former leader's bid to secure his party's backing to retake the White House.

Senator Tim Scott appeared on stage with the ex-president at a rally in New Hampshire, whose residents vote in the state's primary on Tuesday.

"I came to the very warm state of New Hampshire to endorse the next president of these United States, president Donald Trump!" said Scott, who was visiting the northern state during a bitter cold snap, to a chorus of cheers.

"We need Donald Trump," Scott said. "We need a president who unites our country."

The South Carolina lawmaker was in the race for the nomination until November 12 when he withdrew, declining to endorse any other candidate.

He had hoped to become the first Black Republican president, but struggled to rise above the pack in the party's crowded field.

Regularly polling in sixth place among Republican primary candidates, the 58-year-old drew only around two to three percent of the vote, according to the RealClearPolitics average of major opinion polls.

His backing should boost Trump's so-far dominant effort to fend off challenges for the nomination from former UN ambassador Nikki Haley and Florida Governor Ron DeSantis.

The endorsement is likely a bitter pill for Haley, who is from Scott's home state and served as its governor.

CNN reported that Trump had been in discussions with Scott to secure his backing before South Carolina holds its primary election on February 24, but that the announcement was brought forward after Haley saw a bounce in support.

"He's a fantastic man," the scandal-plagued Trump said of Scott. "Having his endorsement means a lot."

"We have to unify. We have to go after these crazy people that we're dealing with," he added, before launching into fierce critiques of Haley.

During his campaign, Scott frequently underlined his Christian faith and the conservative values he learned growing up in a poor, single-parent household.

He was one of five Republicans appearing in the third televised Republican debate last November, as challengers for the nomination sparred over Ukraine, China, abortion and the future of the party.

Scott has expressed no interest in becoming a running mate to any of the remaining candidates, saying that being vice president "has never been on my to-do list for this campaign."