US presidential rivals Barack Obama and Mitt Romney are approaching the final day of their election battle in a frantic fight for swing state votes.
Mr Obama is scheduled to appear in Madison, Wisconsin, accompanied by Bruce Springsteen, before going on to Iowa and Ohio.
Mr Romney is due in Florida - where polls suggest he is ahead - in Virginia, New Hampshire and Ohio.
Analysts say the election will come down to a handful of swing states.
Mr Obama and Mr Romney are running almost neck-and-neck in national polls, but polls of many key battlegrounds show Mr Obama narrowly ahead.
However, neither camp is exuding absolute confidence, the BBC's North America editor Mark Mardell reports.
The campaign has been most intense in Ohio, which no Republican has ever lost and still made it to the White House.
The pair spent Sunday addressing crowds across the country, with Mr Romney speaking in Pennsylvania, a state his aides insist he can now win on Tuesday.
Mr Obama held rallies in New Hampshire and Florida and carried on to Ohio and Colorado in the evening.
In Florida, Democrats have filed a legal case demanding an extension of time available for early voting, citing unprecedented demand.
In Ohio, Republican election officials will go to court on Monday to defend an 11th-hour directive to local election officials.
Last month, a federal appeals court reinstated early voting on the last three days before Tuesday's election.
The ruling overturned a state law saying early voting should end on the Friday before the election, making an exception only for voters living overseas and for military personnel, who tend to favour Republican candidates.
Critics say this potentially favours the Obama camp.
A final poll published on Sunday by Ohio's Columbus Dispatch gave Mr Obama a 2% lead - 50% to 48% - over his rival, within the margin of error.
Both candidates visited the Buckeye State on Sunday, with Mr Romney telling crowds in Cleveland that Mr Obama has failed in his pledge to be a "post-partisan" president and criticising his record.
"He's been divisive, blaming, attacking, dividing and - by the way - it's not only Republicans that he refused to listen to, he also refused to listen to independent voices."
Later on Sunday, he spoke in Morrisville, Pennsylvania, his first visit there in the final stages of the campaign.
Democrats say the Romney team's last-minute decision to campaign in the state is a sign of desperation, but polls do show a tightening race.
"The people of America understand we're taking back the White House because we're going to win Pennsylvania," Mr Romney told the crowd in Morrisville.
Mr Obama made another appearance in Cincinnati, Ohio, where Stevie Wonder opened a huge evening rally.
Earlier in the day at a rally in Concord, New Hampshire, Mr Obama said: "We have come too far to turn back now."
He said he would work across party lines to break the political gridlock in Washington, but would not compromise on priorities such as healthcare and college financial aid.
Activists have been stepping up efforts across the crucial swing states.
In Wisconsin, student volunteers have been putting in 14-hour days in an effort to deliver the state for Mr Obama, the BBC's Paul Adams reports from Madison.
An opinion poll on Sunday for ABC News and the Washington Post put the two candidates at 48%, with even voters who term themselves independents split evenly on 46%.
Mr Romney remains favoured among whites, seniors and evangelical Christians; Mr Obama among women, non-whites and young adults.
The president also remains slightly ahead in most of the nine-or-so swing states that will determine the election.
Opinion polls published on Saturday showed him well-placed in Iowa, Nevada and Ohio, but most remain within the polls' own margins of error.
The election is run using an electoral college.
Each state is given a number of votes based on its population.
The candidate who wins 270 electoral college votes becomes president.