US Democratic presidential front-runner Barack Obama on Tuesday spurned an offer of a “dream ticket” from Hillary Clinton as the two bitter rivals clashed in Mississippi in their latest battle to reach the magic figure of 2,025 delegates required for the party nomination.

“I don’t know how somebody who is in second place is offering the vice presidency to somebody who is in first place,” he told a rally in Columbus, Mississippi.

Obama leads by about 100 delegates after 45 rounds of nail-biting Democratic contests ahead of the primary in Mississippi.

“I want everybody to be absolutely clear I am not running for Vice-President. I am running for the President of United States of America. I am running to be the Commander-in-Chief,” Obama, the Illinois senator who aspires to be the first African-American President of the US, asserted, spurning Clinton’s offer to be her number two.

The Clinton campaign has repeatedly suggested a “dream ticket”, saying that combining the two Democratic party candidates might be a possibility.

Obama leads in the fight for delegates, 1,553 to 1,438, but neither candidate is close to the 2,025 delegates needed to clinch the Democratic presidential nomination in August.

With the high-voltage campaigns of New York Senator Clinton and Obama battling for every delegate in the tight race, the political spotlight is on a state not used to being the centre of such attention, US media reports said.

Mississippi, which has 33 delegates up for grabs in the primary on Tuesday, has not voted for a Democratic candidate in a presidential election in 32 years. Obama has been campaigning in Mississippi since Monday while rival Clinton made a quick tour through the state on Thursday and Friday. Former President Bill Clinton also campaigned for his wife in Mississippi over the weekend.

Obama won the caucuses in Wyoming on Saturday, taking seven of the 12 delegates at stake. Mississippi could make it two in a row for Obama considering that he has a double-digit lead over Clinton in the latest state opinion polls.

Interestingly, Mississippi has a 36 per cent proportion of African-Americans, the highest in the country.

And black voters make up nearly 70 per cent of registered Democrats. Those numbers appear to benefit Obama, who has overwhelmingly won the African-American vote so far this primary season.

However, the Clinton camp is not conceding. While the odds are against a victory in Mississippi, her campaign is hoping they can come out of the contest with a decent amount of delegates.