Republican front-runner Mitt Romney cruised to an easy victory in Nevada on Saturday, crushing his three remaining rivals and taking firm command of the party's volatile presidential nominating race.

Romney captured 44 per cent of the vote with about 43 per cent of precincts counted, taking about a 20-point lead over his closest rivals, former US House Speaker Newt Gingrich and US Representative Ron Paul, who were battling for second place.

The victory was Romney's second in a row and his third in the first five contests in the state-by-state battle to find a Republican challenger to President Barack Obama in November's general election.

It propels Romney into the next contests – in Minnesota, Colorado  – and Missouri on Tuesday – on a huge wave of momentum.

Gingrich held a news conference after the results were announced to head off any speculation that he might put an early end to his campaign.

"I'm not going to withdraw," Gingrich told reporters, repeating his frequent vow to continue his campaign all the way to the nominating convention in Florida in August. "I'm actually pretty happy with where we are."

Romney, a former Massachusetts governor, took control of the Nevada contest early after recapturing his front-runner status with a convincing win over Gingrich in Florida last Tuesday.

He benefited from a huge financial and organisational edge in Nevada, which he won with 51 per cent of the vote during his failed 2008 presidential bid. With a faltering economy and a big bloc of Mormon voters, the state was friendly terrain for Romney, a Mormon and former head of a private equity firm.

Romney stressed his business background as a cure for the state's ailing economy, which suffers from the country's highest unemployment rate, 12.6 per cent in December, and the highest home foreclosure rate.

Entrance polls in Nevada showed that was a persuasive argument, with the economy ranking as the top issue and Romney winning nearly two-thirds of the voters who listed it as their top concern.

"America needs a president who can fix the economy because he understands the economy, and I do and I will," Romney told cheering supporters at a Las Vegas casino hotel, aiming his criticism at Obama and ignoring his Republican rivals.

The entrance polls showed Romney won a wide cross-section of Nevada voters, capturing moderates, conservatives, men, women, Tea Party supporters and those who believed the most important quality in a candidate was the ability to beat Obama.

Romney hopes Nevada will kick off a February winning streak that could position him for a knockout blow to Gingrich during the 10 "Super Tuesday" contests on 6 March – or sooner.

In addition to Tuesday's contests, Maine will wrap up its weeklong caucuses next Saturday, while Arizona and Michigan hold their contests on 28 Feb.

Romney won Colorado, Minnesota, Maine and Michigan in 2008. He came in second in Arizona to native son and eventual nominee John McCain, an Arizona senator. He finished third in Missouri.

Gingrich hopes to hang in the race until March, when there will be contests in several southern states where the former Georgia congressman and US House of Representatives speaker believes he can do well.

He said his goal was to pull approximately even with Romney in delegates after the Texas contest in early April.

Gingrich campaigned in Nevada but did not spend any money on advertising in the state. Former US Senator Rick Santorum of Pennsylvania, who finished a distant fourth in Nevada, skipped the state entirely.

Santorum said the race would begin to open up as it moved past the first five states, where Romney had an organisational advantage.

"We think this is an opportunity for us to begin to turn this race," he told CNN. "The more this race goes on, the more people see we present the best chance to win this."

Nevada's caucuses were held at 125 sites around the state, with voters breaking up into small groups by precinct to tout their candidates and debate their choices. Several Romney supporters said they backed him because he could win in November.

"I think he's the only one who can beat Obama," said George Peterson, a retired Air Force veteran who attended a caucus at Chaparral High School in Las Vegas.

Gayle Darin, an executive assistant at the Bellagio hotel, said she thought it was time for Republicans to pick a candidate and begin to focus on Obama.

"A lot of people have rallied behind Romney now," she said. "We've got to step up and get Obama out of office."