US election: Obama and Romney deadlocked for final push
The US presidential candidates are in the thick of the final two days of campaigning, with the outcome still too close to call.
At a rally in New Hampshire, Democratic President Barack Obama said: "We have come too far to turn back now."
"We're Americans - we can do anything," Republican Mitt Romney told a crowd in the swing state of Ohio.
The latest ABC News/Washington Post survey suggests the pair are level with 48% of support.
Mr Romney is also visiting Ohio, Pennsylvania and Virginia, while Mr Obama is going on to Florida, Ohio and Colorado.
Both Mr Obama and Mr Romney are showing signs of exhaustion as they continue their last-gasp dash to seal the deal with undecided voters in the marginal battleground states that will determine the winner.
Former President Bill Clinton was also suffering as he joined Mr Obama at a rally in Virginia on Saturday, saying he had "given my voice in the service of my president".
Speaking in Concord, New Hampshire, Mr Obama 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.
Mr Romney said in his address to a rally in Des Moines, Iowa: "The only thing that stands between us and some of the best years we can imagine is a lack of leadership - and that's why we have elections."
'Love of country'
Campaigning in New Hampshire on Saturday, Mr Romney criticised Mr Obama for saying that voting would be their "best revenge" on the Republicans.
"Vote for revenge?" said Mr Romney. "Let me tell you what I'd like to tell you: Vote for love of country. It is time we lead America to a better place."
Later, in Colorado Springs, the Republican challenger told supporters that Tuesday's election would be "a moment to look into the future, and imagine what we can do to put the past four years behind us".
"We're that close right now," he said. "The door to a brighter future is there."
The BBC's Bridget Kendall, in the bellwether state of Ohio, says the campaigning there has been at its fiercest. No Republican has ever been elected president without first winning Ohio.
But, she asks, when there has been so much pressure on people to vote early and when all but a tiny fraction of likely voters have made up their minds, how much difference will all this frantic eleventh-hour campaigning make?
Speaking to our correspondent, two voters echoed the country's split on the candidates.
Defence contractor Derek Maddox said: "I'll be voting for Mr Romney... At least he has a plan, for turning the economy round and getting jobs. He's proved he can do it many, many times."
However, retired teacher Anita Hildegren, a registered Republican, said she would vote for Mr Obama: "Maybe not everything got done, but a lot..."
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 evangelicals; Mr Obama among women, non-whites and young adults.
Mr Obama 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.
The BBC will be providing full online live results of the US presidential election on 6 November. More details here