The battle for the Republican Party crown moves into new territory Saturday, with the "reddest of the red" states, conservative heartland Kansas, heading for the polls amid attempts by Rick Santorum to hobble Mitt Romney's slow march forward.

In normal times, Saturday's caucuses in Midwestern Kansas would merit only a passing mention, but with no clear Republican candidate yet to take on Democrat President Barack Obama in November polls, all is still to play for.

"We're very much on the candidates' radar because Super Tuesday has come and gone and we still don't know who our nominee is," said Lora Cox, executive director of the Sedgwick County Republican Party.

"We are definitely the heartland for conservative thought," she said, adding, "I anticipate a big turnout of conservative voters on Saturday."

Ultra-conservative Kansas is an unlikely match for Romney, and the former governor of liberal Massachusetts has stayed away, focusing instead on Tuesday's primaries in the key southern states of Alabama and Mississippi.

Although Romney consolidated his pole position in this week's slew of votes, he failed to knock either Santorum or former House speaker Newt Gingrich out of the race. Libertarian Texas congressman Ron Paul is also still hanging on, even though he has yet to win a single contest.

No polls have been carried out in Kansas, but most observers believe Santorum's tough right-wing message will win over conservatives -- although the race could still be muddled, according to some.

In Wichita, Santorum lumped Obama and Romney together while likening himself to former president Ronald Reagan.

"That guy who was too conservative -- you remember him?" Santorum said to cheers from several hundred supporters gathered in an airplane hangar. "That guy who talked about the sanctity of human life and the importance of marriage in America."

So far Romney is leading the pack overall, having won about a third of the 1,144 delegates needed to secure the party's nomination, after 23 contests in the Republicans' complex state-by-state race.

Kansas Republican Governor Sam Brownback showed up at Paul's and Santorum's speeches on Friday, but did not endorse either.

He said he might endorse one of the contenders after the vote Saturday and predicted the election could make a difference.

"I think it will help to build momentum, and nobody has this won, so momentum's pretty important," he said.

There are 40 delegates at stake in Kansas, and a further 18 split between the far-flung US territories of Guam, Northern Marianas and the Virgin Islands which also hold votes on Saturday.

The bigger prizes are at stake on Tuesday, when Alabama with 50 delegates, Mississippi with 40 and Hawaii with 20 will go to the polls.

"Santorum's social conservatism would be expected to play well with Deep Southern voters," Charles Franklin, co-founder of and a professor at Marquette University Law School, told AFP.

"But, stylistically, Gingrich with his long history in the South maybe is a little more appealing than Santorum's Yankee charm from Pennsylvania."

Two small polls released Friday predicted a tight race in Alabama between Romney, Gingrich and Santorum, narrowly giving the edge to Gingrich.

In Mississippi a poll by Rasmussen Reports gave Romney 35 percent of the vote, with Santorum and Gingrich both on 27 percent.

At a rally Friday in Jackson, Mississippi, Romney went on the attack against Obama, saying: "We've gone from 'yes we can' (in 2008) to 'it's not my fault'. 'It's not my fault' is his new campaign slogan."

But Troy Gibson, associate professor of political science at the University of Southern Mississippi, said he thought a Romney win in Mississippi unlikely.

"I just don't think he has the enthusiastic base that he would need to pull those out," he said.

Under pressure to drop out and clear the way for Santorum, the former House speaker, who won handily on Tuesday in his home state of Georgia, has said the neighboring states of Alabama and Mississippi are "must-wins".

Buoyed by the polls, Gingrich's campaign said it was boosting spending on advertising in the two states.

"Mississippi has been extremely receptive," said Gingrich's state campaign chairman Scott Brewster. "We feel we have momentum and are gaining momentum. Each stop has gotten bigger and bigger, and so we feel really optimistic for Tuesday."

Meanwhile, Romney late Friday claimed victory in caucuses in the US Pacific territory of Guam, saying he had secured the support of all nine delegates at stake there.

"The people of Guam have always stood bravely for America and the values we hold dear," Romney said in a statement. "I am honored to have won the Guam caucuses, an important milestone in my quest to restore America to the principles and practices that made us great."

The former Massachusetts governor did not campaign in Guam personally, but sent his son Matt to the island to campaign on his behalf.

The official vote tally from the territory was not immediately available.