Rick Santorum has picked up victories in the southern states of Mississippi and Alabama to consolidate his status as the leading conservative candidate for the Republican US presidential nomination.
The former Pennsylvania senator, who is challenging long-time frontrunner Mitt Romney for the right to take on Barack Obama in November's election, claimed 33 per cent of the votes in the Mississippi primary, with 96 per cent of ballots counted.
"We're on our way to victory tonight; we're on our way to victory in this election,'' Santorum exulted before cheering supporters in Lafayette, Louisiana, which holds its primary March 24. He said it was time for conservatives to unite in an effort to defeat Romney.
Newt Gingrich, the former House speaker who has been eclipsed by Santorum's rise as the preferred candidate in the Republicans' conservative heartlands, finished second on 31 per cent, followed closely by Romney at 30 per cent.
Santorum earlier won the Republican primary in Alabama with 35 per cent of the vote. Gingrich had 30 per cent and Romney 28 per cent.
Gingrich has been hoping to shore up his flagging campaign with a win in the South by drawing on his ties to the region, and the results if confirmed could increase the pressure on him to withdraw from the race.
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Although Gingrich and Santorum have urged each other to get out of the race, Gingrich indicated in a radio interview on Tuesday that the pair could form a united front against Romney.
Gingrich, however does not seem ready to stand aside.
"I've stayed in this race for two reasons," he said. "I do not believe the two other candidates can beat President Obama."
Romney has opened a big lead in delegates in the Republican race to pick a challenge Obama in the November 6 election, but he has been unable to capture the hearts of conservatives who distrust him for some of the moderate stances he took as governor of liberal Massachusetts.
Romney, however, rejected the notion his inability to put away his conservative rivals would mean none of the candidates would have the 1,144 delegates needed to clinch the nomination before the convention in August.
He said Santorum was reaching the "desperate end of his campaign" and faced a steep climb to catch up in the race for delegates.
Romney currently has about 454 delegates; Santorum 217 and Gingrich 107.
Al Jazeera's Alan Fisher reporting from Washington "This was a good night for Rick Santorum, but for Mick Romney, he may have the delegates but there is a concern."
Fifty delegates are at stake in Alabama and 40 in Mississippi. There also will be caucuses in Hawaii, where 17 delegates are at stake. In each of the states, candidates are awarded delegates proportionally based on their vote totals.