Hillary Clinton is heading for a big victory over Barack Obama in West Virginia's primary despite diminishing hopes it could turn around her faltering Democratic presidential bid.

Meanwhile, Mr Obama, with the Democratic nomination virtually locked up, set his sights on November's general election battle against Republican John McCain.

Mrs Clinton campaigned heavily in West Virginia, with polls showing her leading by as much as 40% points.

Mr Obama did little more than pay a quick stop to a state poised to shun him. West Virgina has large numbers of working-class whites, and few of the black voters that have helped propel Mr Obama to wins elsewhere.

His focus on general election swing states reflected the electoral figures overwhelmingly in his favour. He may be a few weeks from clinching the Democratic nomination irrespective of what happens in West Virginia or Kentucky, another Mrs Clinton stronghold that votes next week.

Only 28 delegates are at stake in West Virginia, and under party rules Mr Obama would still get at least a few even if he loses.

Mr Obama has already picked up more than two-dozen superdelegates since last Tuesday when he routed Mrs Clinton in North Carolina and narrowly lost to her in Indiana.

Mr Obama is now mathematically within reach of clinching the Democratic nomination by the end of the primary season on June 3 - even if he loses half of the remaining in five states and Puerto Rico.

Though Obama has a strong lead in elected delegates, he still needs the support of the superdelegates to reach the 2,025 total needed to secure the nomination.

That means the superdelegates - the nearly 800 party leaders and elected officials who may vote for whichever candidate they choose regardless of the state primary or caucus results - are essential to capturing the nomination.