Republican primaries: Jon Huntsman to end bid
Jon Huntsman is to end his campaign to win the Republican presidential nomination, US press reports say.
He finished third in last week's New Hampshire primary and had been struggling ahead of this week's South Carolina primary.
Mr Huntsman had hoped for an upset in New Hampshire but polled only 17%.
He will announce his withdrawal in South Carolina on Monday and endorse front-runner Mitt Romney, campaign officials said.
Primaries and caucuses will be held in every US state over the next few months to vote on a Republican candidate before the eventual winner is crowned at the party convention in August.
Mr Huntsman, 51, is a former governor of Utah and served as President Barack Obama's first ambassador to China.
A fluent Chinese speaker, in the early 1990s he became the youngest head of a US diplomatic mission for a century when he was appointed ambassador in Singapore.
But his campaign for the Republican nomination failed to gain momentum, hardly registering in national opinions polls with only 1% or 2%.
"The governor and his family, at this point in the race, decided it was time for Republicans to rally around a candidate who could beat Barack Obama and turn around the economy," campaign manager Matt David told the New York Times.
"That candidate is Governor Mitt Romney."
His withdrawal comes after he gained the endorsement of South Carolina's largest newspaper The State, which said that he and Mr Romney were the "two sensible, experienced grown-ups in the race'', but that Mr Huntsman was "more principled" and offered "a significantly more important message''.
Mr Romney won nearly 40% of the New Hampshire vote last Tuesday, but faces a stern test in South Carolina this week.
The staunchly Republican state has a history of backing the eventual nominee in its primary.
Mr Huntsman's exit will leave Ron Paul, Rick Santorum and Newt Gingrich as the three main candidates chasing Mr Romney's lead.
After his handsome win in New Hampshire, Mr Romney is seen as more vulnerable in socially conservative South Carolina, and his Mormon faith may be a disadvantage among the many evangelical and other conservative Christians in the state.
In a statement released on Monday morning, Mr Gingrich said Jon Huntsman's withdrawal meant the US was "one step closer to a bold Reagan conservative winning the GOP nomination" - terms in which he frequently describes his own candidacy.
Televised debates will be held in South Carolina on Monday and Thursday, before the primary vote on Saturday.