Washington: The crucial Republican presidential primary in the two southern States of Mississippi and Alabama on Tuesday is headed for a close finish with the two leading candidates running neck to neck, according to latest opinion polls.

According to one poll, in Mississippi, front runner Mitt Romney led Newt Gingrich, the former Speaker of the US House of Representatives, 34 per cent to 32 per cent, which was within the margin of error.

In Alabama, according to another poll, Gingrich led over Romney 34 per cent to 31 per cent, also within the margin of error.

Rick Santorum, the former Pennsylvania Governor, who is so far second in the race in terms of the delegates and number of States won after Romney, is trailing behind by more than 10 points in both the Alabama and Mississippi.

According to CNN's estimate, Romney has 458 delegates, compared with 203 for Santorum, 118 for Gingrich and 66 for Ron Paul, the Congressman from Texas.

To win the Republican nomination, a candidate needs 1,144 delegates.

On Monday Santorum told reporters that it is going to be a "very tight contest" in Mississippi and Alabama and lowered his expectations from these two Republican primaries.

In all 90 delegates are at stake in both the States. "I don't think we have to win, I just think we have to continue to do well. I'm going into Newt's backyard, and obviously Governor Romney is coming off of a big Super Tuesday," Santorum said.

"We've got to come in here and do well, and I think from all the polls we're doing very well. The math going forward is going to be better for us," he said.

Romney, however, exuded confidence that the Tuesday's victories would give him an inaccessible lead over his rivals.

"We’re closing the deal. State by state, delegate by delegate. We're winning this and I expect we're going to get the nomination," he said.

"Ultimately I believe I'm going to become the nominee, and the reason is we want someone who can beat Barack Obama," Romney said.

On Monday he appeared with comedian Jeff Foxworthy, who endorsed him over the weekend.

"Mitt is the right guy for the job. It's time to get united behind one candidate, the candidate that I believe has the best chance of beating Barack Obama in the fall," Foxworthy said.

A day earlier Gingrich had said that he will win both the States and that Romney was a weak candidate.

Gingrich has so far won only two States – South Carolina and Georgia.