Barack Obama took a big stride towards the Democratic Party's presidential nomination on Tuesday with a thumping victory over Hillary Clinton in North Carolina while fighting hard in Indiana.

CBS News said the former first lady was on course to win in Indiana, and Obama acknowledged that she appeared to have won the state. But other US networks said the outcome was still too close to call.

Addressing rapturous supporters in Raleigh, North Carolina, Obama said the state's voters had rebuked "the politics of division and distraction," "the same old negative attacks" and "gimmicks" — a veiled assault on Clinton.

The Illinois senator, bidding to be the country's first black president, said he was now fewer than 200 delegates away from securing the Democratic nod to take on Republican John McCain in November's general election.

Obama denied the Democrats would go into the election "inalterably divided" because of the bitter rancor that has engulfed his epic battle against Clinton.

"Yes, each side desperately wants their candidate to win," he said in his victory speech in North Carolina. "But ultimately, this race is not about Hillary Clinton or Barack Obama or John McCain.

"This election is about you — the American people — and whether we will have a president and a party that can lead us toward a brighter future."

Clinton headed for disappointment

With 52 percent of the vote counted in North Carolina, Obama was projected by US media to have 58 percent to 42 percent for Clinton, on her own historic quest to be the first woman in the Oval Office.

With 74 percent of the vote counted in Indiana, she was up 52 percent to 48 percent for Obama. But pundits said several city districts heavy with African-American voters had yet to declare.

The two states were the biggest nominating contests left in the Democrats' White House tussle after months of back and forth that will culminate in the final primaries on 3 June.

CNN exit polls said the African-American Obama, buffeted by weeks of controversy over racially tinged remarks by his former pastor, had won more than one-third of white voters in North Carolina.

Clinton meanwhile looked headed for disappointment after aiming for a "game-changer" in North Carolina that could transform her prospects against Obama.

A total of 187 pledged delegates were on offer in the two states — 115 in North Carolina and 72 in Indiana. After Tuesday, 217 elected delegates will be up for grabs in the remaining six contests ending in early June.

'I don't make predictions'

Clinton's camp admits she cannot overtake Obama in the count of pledged delegates who will formally anoint the nominee at the Democratic convention in August.

So she is trying to persuade the nearly 800 Democratic "superdelegates," who are free to vote for either candidate, that her inexperienced rival would go down in flames against McCain.

Clinton refused to say whether she would pull out of the race if she lost both contests. "I don't make predictions," she said, as she toured the famed Indianapolis Motor Speedway with Indy 500 driver Sarah Fisher.

"Life is unpredictable, racing is unpredictable, politics is unpredictable."

Clinton also raised the prospect of carrying on after the end of the nominating calendar, a scenario many Democrats fear could split the party and hand victory to McCain.

Looking ahead to June, she said "if we haven't done it already, we are going to have to resolve Florida and Michigan. They were legitimate elections, people came out and voted."

She said the true finish line of the presidential race was 2209 delegates — including Florida and Michigan, whose pro-Clinton results were voided in an argument with Democratic bosses about the timing of the states' primaries.

Contradicting Clinton, Democratic National Committee chairperson Howard Dean said the delegate target remained 2025.

"There's going to be a compromise is what I would predict," he said on MSNBC, ahead of a 31 May meeting of the DNC's rules committee on the Florida-Michigan headache.

"We'll have a nominee by the end of June," Dean added, playing down fears of a convention brawl in August.