President Barack Obama set off on a marathon, two-day campaign journey Wednesday — touching down in five states and making an appearance on a popular late-night television program — as he tries to break out of the tight race with Republican challenger Mitt Romney with just 13 days left before the Nov. 6 election.

Obama is hammering Romney over his abrupt shift to moderate positions at home and abroad after months of campaigning as a hard-right conservative. Romney, looking to sustain momentum from his victory in the first presidential debate three weeks ago, says Obama has failed to bring the economy back to full speed after the Great Recession.

In remarks released Wednesday, Obama predicted he'll reach agreement with lawmakers to reduce the U.S. deficit in the first six months and overhaul immigration law within the first year if he's re-elected. His comments to The Des Moines Register were originally off the record, but his campaign agreed to release a transcript under pressure from the newspaper.

Obama said if he wins a second term, a big reason will be because Republicans have "so alienated the fastest-growing demographic group in the country, the Latino community."

The Romney campaign criticized Obama's comment in the interview that he had no regrets focusing on health care instead of the economy during his first two years in office. The president rejected the idea that he could have accomplished more on the economy instead.

"In the face of a struggling economy, President Obama took his eye off the ball, and spent over a year focused on passing Obamacare," Romney spokeswoman Amanda Henneberg said in a statement.

Republican presidential nominee Mitt Romney said Barack Obama neglected the economy while focusing on healthcare. (Brian Snyder/Reuters)

Both men are making extraordinary efforts to sway the small pool of undecided voters, particularly in key battleground states such as Ohio and Iowa where early voting is already under way.

Obama planned a short stop in Chicago on Thursday to cast his own vote — the first time an incumbent president has opted for early voting.

The election map has shrunk to no more than nine of the 50 U.S. states that do not reliably vote either Republican or Democrat. The states assume outsized importance because the president is chosen according to state-by-state contests, not the national popular vote.

Senator's rape comments darken Romney campaign

Romney's campaign was challenged Wednesday after a Republican Senate candidate angered voters with comments on rape and abortion. Richard Mourdock told a live television audience this week that when a woman becomes pregnant during a rape, "that's something God intended."

As Mourdock stood by his statement and said it was twisted around, Romney's campaign at first distanced itself from him and then said Wednesday that Romney still supports him.

Women voters are key to this year's election.

Obama was planning to cover 8,500 kilometres on Wednesday in the most-travelled single day of his re-election bid. He was going from Washington to Iowa, Colorado, California and Nevada, and then overnight to Florida. It was the first time Obama was spending the night flying on Air Force One for a domestic trip.

Romney, too, was picking up the pace, campaigning Wednesday in Nevada and Iowa before a three-stop campaign in Ohio on Thursday.

Obama's campaign has insisted that the president was holding on to a slight lead in most of the nine battleground states — Nevada, Colorado, Iowa, Wisconsin, Ohio, Virginia, North Carolina, Florida and New Hampshire

Obama seen as more trustworthy

Obama's challenge is to convince voters who may be hurting financially that he is better qualified to lead the country back to economic prosperity than Romney, who made a fortune as the head of a private equity firm.

'You know I say what I mean, and I mean what I say.'—Barack Obama

Obama is trying to capitalize on polls that show voters see him as more trustworthy than Romney. A Washington Post/ABC News poll last week showed 55 per cent of likely voters said Obama is "honest and trustworthy" compared to 47 per cent who felt that way about Romney.

"You know me. You know I say what I mean, and I mean what I say," Obama told an Iowa crowd on Wednesday. "With your help, I've kept the commitments that I made."

Obama's remarks came after Monday night's third and final presidential debate, where Romney revealed dramatic shifts to the centre on foreign policy and largely expressed agreement with how Obama has conducted U.S. foreign policy.

The Obama campaign responded this week to criticism that the president had failed to articulate his second-term vision, producing a 20-page booklet called the "Blueprint for America's Future" outlining his proposals, including spending more on education, boosting U.S. manufacturing jobs and raising taxes on the wealthy