WASHINGTON - Rick Santorum overwhelmingly won the Kansas presidential caucuses Saturday, hoping to blunt front-runner Mitt Romney's momentum in the grinding campaign for the nomination to oppose President Barack Obama in the November election.

But Romney countered with wins in Wyoming as well as in Guam, the Northern Mariana Islands and the U.S. Virgin Islands.

Santorum, a former Pennsylvania senator, was considered the favourite in Kansas, where his staunch opposition to abortion and gay marriage resonated with the state's large bloc of evangelical voters. He hoped his victory would give him an advantage heading into Tuesday's unexpectedly pivotal primaries in the southern states of Alabama and Mississippi where polls show he is dividing the most conservative vote with Newt Gingrich.

Gingrich, struggling for survival in the race, can ill afford a loss in either Mississippi or Alabama. Romney is seeking a Southern breakthrough to demonstrate an ability to win the support of evangelical voters.

For his part, Santorum hopes to knock Gingrich out of the race and finally emerge as Romney's sole challenger from the right.

Final returns in Kansas showed Santorum with 51 per cent support, far outpacing Romney, who had 21 per cent. Gingrich had 14 per cent and Ron Paul trailed with 13 per cent.

Santorum picked up 33 of the state's 40 delegates at stake, cutting slightly into Romney's overwhelming advantage.

"Things have an amazing way of working out," Santorum told supporters in Missouri, where he traced his campaign through a series of highs and lows. He called his showing in Kansas a "comfortable win."

In sparsely populated Wyoming, Romney won at least six of the 12 delegates at stake, Santorum three, Paul one. Uncommitted won one, and a final delegate remained to be allocated.

Romney did not campaign in Kansas. Santorum and Paul, a Texas congressman, both made stops in the state in the days leading to the caucuses.

Gingrich cancelled a scheduled trip to Kansas late in the week to concentrate on the primaries in Alabama and Mississippi, which the former speaker of the House of Representatives considers friendlier territory. Gingrich, who represented a Georgia district in the House for two decades, attended five campaign events Saturday in Alabama and stressed his Southern connections.

Polls show a close three-way race in both southern states, particularly Alabama, and Romney, Gingrich and Santorum all added to their television advertising for the race's final days.

Romney has been benefiting so far because the more conservative vote has been divided between Santorum and Gingrich, enabling him to defeat Santorum by a few percentage points in such key states as Ohio and Michigan.

The former Massachusetts governor continues to fight skepticism among Republican voters about his past, more moderate, views on such sensitive social issues as abortion. Santorum styles himself as the true conservative in the race, but he lacks the campaign cash and organization that the multimillionaire Romney, the former CEO of a private equity firm, has at hand.

The contests in Kansas and Wyoming left Romney with 453 delegates in the AP's count, more than all his rivals combined. Santorum had 217, while Gingrich had 107 and Paul had 47.

Romney's totals included 22 that he picked up over the weekend in the Virgin Islands, Guam and the Northern Mariana Islands.

A candidate must win 1,144 to clinch the Republican presidential nomination at the national convention in Tampa, Florida, in late August.

The Kansas and Wyoming caucuses had little in common except a shared date on the campaign calendar.

Kansas drew more attention from the White House hopefuls, but not much more, given its position midway between Super Tuesday when Romney won six of the 10 state contests and the Tuesday primaries in Mississippi and Alabama.

An aide to Gingrich said earlier in the week the former House speaker must win both Southern primaries on Tuesday to justify continuing in the campaign.

But Gingrich strongly suggested otherwise on Friday as polls showed a tight three-way contest in Alabama.

"I think there's a fair chance we'll win," the former House speaker told The Associated Press about the contests in Alabama and Mississippi. "But I just want to set this to rest once and for all. We're going to Tampa."

Romney had no campaign appearances Saturday.

Despite his constant campaign message of having the business background to fix the economy -- by far the biggest issue in this election -- Romney has not been able to pull away from his rivals for good.

Meanwhile, Obama's team has renewed confidence about the president's chances of winning re-election because of the divisive Republican campaign and more good news in the latest jobs report. But privately, his advisers know that outside factors in the United States and abroad -- from high gasoline prices to instability in the Middle East -- could still derail his campaign in coming months.

In the latest good economic news, the monthly jobs report released Friday showed employers created 227,000 jobs in February. The unemployment rate held steady at 8.3 per cent, the result of more Americans looking for work as job growth takes hold month by month.

The struggling economy has haunted the president as he seeks a second four-year term in November, and his Republican opponents have hammered the issue in their campaigns. But Obama's approval ratings have been rising along with the economic numbers.