US presidential rivals John McCain and Barack Obama are giving one last push to secure votes with just a day to go until the election.

Republican Mr McCain is trailing Democrat Mr Obama in the polls by more than six points in the latest average of national polls.

But the McCain campaign insists it has the momentum and could still mount an historic comeback.

The Democrats have unleashed a "persuasion army" of backers scouring their own backyards to encourage people to back Mr Obama.

More than 10,000 volunteers have been knocking on doors in Ohio and expected to hit their one millionth home after a five-day push.

His campaign also reported that Saturday was its largest volunteer day, with more volunteers showing up to work the phones and walk neighbourhood precincts than ever before in the campaign.

"Our volunteers are completely engaged," said Obama campaign spokesman Bill Burton.

At a rally in the state, Mr Obama added: "Go vote right now. Do not delay because we have work to do."

The Republican Party launched the last stage of its "72-hour programme" with volunteers descending on competitive states for the final stretch.

Rich Beeson, the political director of the Republican National Committee (RNC), said: "There's no doubt that we've got an uphill battle."

But he added: "I'm not going into election day with any trepidation that they've put any state away" by banking early votes.

"We still have a lot of voters that we can and will turn out."

About 27 million absentee and early votes were cast in 30 states as of Saturday night, more than ever before, and Democrats outnumbered Republicans in pre-election day voting in key states.

Mr Obama is targeting Florida, North Carolina and Virginia, while Mr McCain began his day in Florida and will go to Virginia, Indiana and New Mexico, before finishing off in Nevada.

Some of the closest battleground states are Florida, Ohio, North Carolina, Missouri, and Indiana.

All were won by Republican president George Bush, but have been made competitive by Mr Obama's record-shattering fundraising operation which saw his campaign bring in £93.1 million in September alone.

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