U.S. presidential hopeful Barack Obama handily defeated rival Hillary Clinton Tuesday in Mississippi's Democratic primary, the final contest before next month's high-stakes race in Pennsylvania.

Democratic presidential hopeful Barack Obama shakes hands after having breakfast at Buck's Restaurant in Greenville, Miss., on Tuesday.
(Alex Brandon/Associated Press)

Obama's victory was declared by CNN and the Associated Press just before 8:30 p.m. ET.

Obama, an Illinois senator, was expected to win the primary. Even Clinton's campaign had conceded earlier in the week that its candidate had little chance to win in Mississippi, where 33 delegates are up for grabs.

While Clinton, a New York senator and former first lady, campaigned in the state last week, she was in Pennsylvania on Monday, already gearing up for that April 22 primary, where 158 delegates are at stake.

But Obama spent Monday in Mississippi, where its large black electorate was expected to help solidify his victory there. He swept the other Deep South states and pulled huge margins among black voters.

"I am grateful to the people of Mississippi for the wonderful support," Obama said in an interview on CNN. "What we try to do is steadily make sure in each state we are making the case for the need for change in this country, and obviously the people in Mississippi responded."

According to exit polls Tuesday night, Obama was winning roughly 90 per cent of the black vote, but only about 25 per cent of the white vote, extending a pattern that carried him to victory in earlier primaries in the Deep South states of South Carolina, Alabama, Georgia and Louisiana.

Late Tuesday, he had picked up at least six delegates in Mississippi, according to the Associated Press count. Another 27 had yet to be awarded.

Obama hints Clinton could be good VP

The race between Obama and Clinton has been tight throughout the primary process, with each candidate attacking the other's policies and ideas. But on Tuesday, Obama insisted he hasn't been nasty.

"We've been very measured in terms of how we talk about Senator Clinton," he said of his campaign team. "I've been careful to say that I think Senator Clinton is a capable person and should she win the nomination, obviously I would support her.

"I'm not sure we've been getting that same approach from the Clinton campaign, but I'm confident that once we decide on a nominee, and go through the convention, that the party's going to be unified."

Obama hinted that he could be persuaded to have Clinton as a running mate, should he win the nomination. He said he would look for a vice-president who would be able to carry on with his vision, should something happen to him during his presidency.

"Obviously, Senator Clinton is a very capable person. As I've said before, she'd be on anybody's shortlist," Obama said.

His comment came a day after he slammed suggestions that he could be Clinton's vice-president. He noted that he has won more states, votes and delegates than Clinton so far, and said it didn't make sense that Clinton's camp could offer the vice-presidency to him when he's clearly winning the race to be the Democratic presidential candidate.

Hoping for momentum after Ohio, Texas

Obama was seeking to regain some momentum on Tuesday after losing three out of four contests, including primaries in Ohio and Texas, last week. But he won the Wyoming caucuses on the weekend and still leads Clinton by more than 100 delegates.

On Tuesday, CNN reported that Obama won the Texas caucuses, where results took a week to compile.

Obama went into Mississippi with 1,579 delegates, to 1,473 for Clinton. It takes 2,025 to win the nomination.

The delegates will choose the Democratic presidential candidate at the party's national convention in Colorado in late August.

With files from the Associated Press