WASHINGTON • Mr Mitt Romney, the 2012 Republican nominee for the White House, has said he will vote for Mr Ted Cruz in this week's Utah primary, all but endorsing the arch-conservative senator as he seeks to derail Mr Donald Trump's nomination bid.

Mr Romney, who has led the charge among party elites to prevent the celebrity billionaire from becoming the Republican standard bearer, said on Facebook that he was encouraging others to vote for Mr Cruz as a firewall against what he called "Trumpism".

"Through the calculated statements of its leader, Trumpism has become associated with racism, misogyny, bigotry, xenophobia, vulgarity and, most recently, threats and violence. I am repulsed by each and every one of these," Mr Romney said.

"The only path that remains to nominate a Republican rather than Mr Trump is to have an open convention," he added, referring to the rare situation in which delegates gather for their party convention with no candidate having the majority needed to seize the nomination outright.

"At this stage, the only way we can reach an open convention is for Senator Cruz to be successful in as many of the remaining nominating elections as possible."

Mr Romney still holds considerable sway in Utah after overseeing the rescue of the 2002 Salt Lake City Olympics, which was in jeopardy amid a bribery scandal.

The state votes on Tuesday along with Arizona.

Mr Trump responded swiftly to Mr Romney, whom he blamed for leading a lacklustre campaign against President Barack Obama four years ago.

"Failed presidential candidate Mitt Romney, the man who 'choked' and let us all down, is now endorsing Lyin' Ted Cruz. This is good for me!" Mr Trump posted to his about seven million Twitter followers.

Of those left in the race, Mr Trump leads with 683 delegates, followed by Mr Cruz who has amassed 421, according to the latest CNN estimate. Ohio Governor John Kasich pulls up the rear with 145 delegates.

Mr Kasich's team insists the governor, who defeated Mr Trump in Ohio last week, is best suited to stop the front runner at the convention, but Mr Romney begged to differ.

"I like Governor John Kasich," he said. "But a vote for Governor Kasich in future contests makes it extremely likely that Trumpism would prevail."

AGENCE FRANCE-PRESSE