WASHINGTON — Mitt Romney scored his third major victory in the Republican presidential race on Saturday as his chief rival for the prize, Newt Gingrich, planned to unveil a new strategy for his flailing campaign.

Romney won the "first in the West" Nevada caucuses with almost 50 per cent of the vote, while Gingrich and libertarian congressman Ron Paul were in a fierce battle for second place.

"This is not the first time you gave me your vote of confidence and this time I'm going to take it to the White House," Romney, who resoundingly won the state during his first run for president four years ago, told his cheering supporters in Las Vegas.

U.S. President Barack Obama came to office apologizing for America while "he should be apologizing to America," he said.

Gingrich, meantime, scheduled a Las Vegas news conference for 11 p.m. EST in Las Vegas, a departure from the more traditional practice of addressing supporters at a campaign rally after caucus results are known.

Word of the news conference spurred speculation that Gingrich might be announcing he's dropping out, especially in light of a remarkably light schedule of events in Nevada after being trounced by Romney in the Florida primary earlier in the week.

The former speaker of the House of Representatives, however, has repeatedly vowed to stay in the race until the Republican National Convention in Tampa in late August. And Romney had long been favoured to win Nevada, with its significant Mormon population.

But rather than dropping out, the Gingrich campaign said it was set to announce plans to refocus his bid for the White House with a delegate-based strategy that will enable him to stay in the race until the convention.

There were no details on how he'd achieve that goal.

Sheldon Adelson, the casino mogul who's already donated millions to Gingrich's political action committee, was to appear with him at the Las Vegas news conference.

Gingrich has had a rough road on the campaign trail since his resounding loss to Romney in Florida following a US$14 million barrage of negative advertising launched against him by pro-Romney forces.

Gingrich's campaign suggested to reporters all week that real estate mogul Donald Trump was about to endorse him; in fact, the mega-mouthed millionaire threw his support behind the former Massachusetts governor on Thursday.

Gingrich also reportedly missed a meeting with Brian Sandoval, governor of Nevada. Sandoval supported Texas Gov. Rick Perry's run for president and was thought to be ready to back Gingrich.

Nonetheless, Gingrich handlers have high hopes for so-called Super Tuesday, a day of multiple caucuses and primaries on March 6. The delegate-rich state of Georgia, in particular, could be fertile ground for Gingrich.

The winning candidate has to win 1,144 delegates to get the nomination. Victories in the early primaries and caucuses generally propel a winning candidate to the later states on a wave of momentum.

Romney's already taken New Hampshire, Florida, and now the Nevada caucuses.

But there are some disturbing signs ahead for the Republicans.

Their intention to hit Obama hard on the economy could be more difficult with promising new jobs numbers that caused the nation's unemployment rate to drop to 8.3 per cent.

And except for South Carolina, voter turnout at the party's primaries and caucuses is down from four years ago, possibly a sign of a lack of enthusiasm for the Republican candidates.