Mr Obama spent the day resting in Chicago. Since decisively winning the North Carolina primary last week, he has increasingly looked ahead to his coming battle with Mr McCain. -- PHOTO: AP

Interviewed on Fox News Sunday, Mr David Axelrod said undecided superdelegates to the party convention who will decide the nomination were opting for Mr Obama, the Illinois senator who would be the first black United States president if elected in November.

'You're going to see people (superdelegates) making decisions at a rapid pace from this point on,' Mr Axelrod said.

'We've been announcing several each day for the last few days. We're going to continue to unfurl these endorsements on a regular basis.'

Mrs Clinton's senior adviser Howard Wolfson, appearing on the same programme, rejected the idea that the campaign was over and predicted victory in the next state primary in West Virginia on Tuesday.

'If Barack Obama wants Hillary Clinton out of this race, beat her. Beat her in West Virginia, beat her in Puerto Rico, beat her in Kentucky,' he said, referring to three of the final six contests for the nomination, all of which favour Mrs Clinton.

But he said if Mr Obama, 46, won the nomination, the New York senator would throw all her support and resources behind him against Republican nominee John McCain.

Mr Axelrod's assessment was shared by former Democratic hopeful John Edwards who has not endorsed either candidate.

Interviewed on the CBS programme Face the Nation, Mr Edwards said Mrs Clinton had improved as a candidate recently but it probably came too late.

Mr Edwards, a former North Carolina senator, said of Mrs Clinton: 'She's been making a pretty compelling case for her candidacy. The problem is, I think, you can no longer make a compelling case for the math. The math is very, very hard for her.' Mrs Clinton, the former first lady, spent Mother's Day campaigning in West Virginia, calling for more progress towards full equality for women.

'Hard work and resiliency are encoded in our genes,' she said, picking up on two qualities she herself has won praise for during the exhausting presidential campaign.

Mr Obama spent the day resting in Chicago. Since decisively winning the North Carolina primary last week, he has increasingly looked ahead to his coming battle with Mr McCain, testing themes he hopes to use in the campaign.

Link to Bush
In an interview with CNN last week that was aired on Sunday, he made it clear he would seek to link Mr McCain to unpopular fellow Republican President George W. Bush.

'Think about what I am going to be running against, the failed policies of the Bush administration which John McCain wants to continue.' Mr Obama said.

Even if she triumphs in the remaining contests, Mrs Clinton, 60, cannot overtake Mr Obama in pledged delegates for the Democrats' August national convention in Denver. The delegates have been allocated proportionately in the state-by-state battles that began in January.

That leaves the decision on which Democrat will face Mr McCain in the November election in the hands of around 800 superdelegates - party leaders and activists free to choose whichever candidate they wish.

The latest delegate count from NBC news gives Mr Obama 1,859 delegates and Mrs Clinton 1,703, while 2,025 are needed to clinch the nomination.

Many Democrats are eager to get the nominating battle over so the party can unite and prepare to face Mr McCain, 71. Some worry the protracted battle is hurting their chances in November by highlighting both candidates' weak points and driving a wedge between their supporters.

Mr Obama has won most support from upscale voters, young voters and blacks. Mrs Clinton's support comes more from working class white voters and Hispanics.

A Los Angeles Times poll this weekend showed both Democrats leading Mr McCain. Mrs Clinton led the Arizona senator 47 per cent to 38 per cent while Mr Obama was ahead 46 per cent to 40 per cent. The margin of error was plus or minus 3 percentage points.

A poll analysis said dissatisfaction with the economy was driving the results, with 56 per cent of respondents naming that as their main issue, a turnaround from six months ago when the war in Iraq was the top concern.

Among voters worried about the economy, a solid majority backed either of the Democrats against Mr McCain. -- REUTERS