Mr Kerry is set to hold an airport rally in Orlando, Florida, before leaving the flashpoint state for the Midwest.

Mr Bush opened his final campaign drive in Ohio, and will sprint through Pennsylvania, Wisconsin, Iowa, New Mexico and then back home to Texas.

Under US electoral law, they are allowed to campaign until midnight, local time.

This comes as five separate polls called the contest a dead heat, ahead of Tuesday’s ballot, while four others gave Mr Bush a slight lead.

Florida is potentially the most vital state, where clinched Mr Bush’s 2000 victory. A poll a week ago gave the president an eight-point lead, however a separate weekend state survey put Mr Kerry three points ahead.

Mr Bush was in Florida where he appealed to the Cuban vote.

“I’m here to ask for your help,” he said. “Tell your friends and neighbours in a free society we have an obligation to vote.”

Mr Kerry too has focused on security.

“The world is waiting for us to lead again, and I know that you will make the choice that will help us take this country to a stronger place. And take the world to a safer place,” he said.

Mr Kerry told the predominantly black congregation Shiloh Baptist church in Dayton, Ohio, that the president’s policies were not in keeping with Mr Bush’s Christianity.

“There is a standard by which we have to live. Coming to church on Sundays and talking about faith and professing faith isn’t the whole deal,” he said.

Mr Bush appealed to wavering Democrat supporters who may feel alienated by Mr Kerry.

“If you are a Democrat who believes your great party has turned too far left this year, I ask you, come and stand with me,” he said.

Analysts believe the tight race in Ohio may this year provide the decider.

Whoever wins there has won the White House in every election since 1964, and no Republican has ever won without it.

Ohio has 20 electoral college votes, and hundreds of thousands of people have lost their jobs since the last election in the state.

Key battleground states:

Florida (27 electoral votes) Won by Mr Bush in 2000 by a narrow 537 votes after a disputed count wound up settled by the US Supreme Court. Mr Bush’s brother Jeb is the state’s governor.

Ohio (20 electoral votes) Midwest state won narrowly by Mr Bush in 2000, who narrowly leads here in most polls. However a flagging economy and job losses could deliver the state to Mr Kerry.

Pennsylvania (21) Mr Kerry slightly leads in this eastern state.

Michigan (17) High unemployment and a bid to ban gay marriage could draw out Republicans in this Midwestern state.

Minnesota (10) Won by the Democrats in seven straight elections, but polls are divided Ralph Nadar could potentially split the liberal vote.

Iowa (7) Half industrial and half rural, Mr Bush won here by only a few thousand votes last election.

New Mexico (5) Lost by Mr Bush by only 366 votes, a burgeoning economy could deliver the south-western state to the president this year.

Nevada (5) A Kerry hopeful, with many residents unhappy over plans to built a nuclear waste storage dump in its Yucca Mountains, however polls show a slight Bush lead.

New Hampshire (4) Polls are split, however Mr Kerry has hopes of snatching it back from the Republicans. Despite being traditionally conservative, New Hampshire voted for Mr Clinton in 1992 and 1996.