Just two days before the US presidential election, US President Barack Obama and Republican Candidate Mitt Romney are making their final pitches in the crucial battleground states that could determine who wins the White House.

Sunday morning, an estimated 14-thousand people packed the streets of downtown Concord, New Hampshire to see Obama make his final plea for support.

Joined by former US President Bill Clinton at an outdoor rally behind the Statehouse, Obama pledged with supporters for four more years, urging them to give his administration a chance to complete the work it has already begun.

"We've made real progress these past four years but New Hampshire, we're here because we know we've got more work to do," Obama said.

"As long as there's a single American who wants a job but can't find one, our work is not yet done. As long as there are families who are working harder and harder but still falling behind, our work is not yet done, as long as there is a child anywhere in New Hampshire, anywhere in this country, who is languishing in poverty and barred from opportunity, our fight has to go on," he added.

With polls showing New Hampshire virtually tied for the two candidates, Obama also went after his opponent, insisting he's not the agent of change he likes to portray himself as.

"We know what change looks like and what he's selling ain't it. It ain't it. Giving more power back to the biggest banks, that's not change. Another five (t) trillion dollar tax cut that favours the wealthy, not change. Refusing to answer questions about the details of your policies until after the election is over, that's definitely not change. That's the oldest trick in the book," he said.

Obama was also holding rallies on Sunday in Florida, Ohio and Colorado; all states that could decide the outcome of Tuesday's election.

Meanwhile, Mitt Romney spent Sunday morning in Iowa, another of the battleground states.

He, too, went after his opponent, claiming Obama's first term was marked by broken promises and empty rhetoric.

"He was going to create jobs, remember that, that was his focus. But instead he focused on Obamacare, which killed jobs. He said he was going to cut the federal deficit in half, he doubled it. He said that unemployment would now be at 5.4 percent, we just learned on Friday it's 7.9 percent," Romney said in Des Moines.

"This is very different than what he promised. His record is very different than his word."

"The question of this election comes down to this: Do you want four more years like the last four years or do you want real change?" Romney asked the crowd of cheering supporters.

Two days before the end, both campaigns were predicting wins in Tuesday's election.

Obama was closing out the campaign with an apparent edge in some key battleground states, including Ohio.

But Romney's campaign was projecting momentum and banking on late-breaking voters to propel him to victory in the exceedingly close race.