Mitt Romney, the multimillionaire businessman and former governor of the northeastern state of Massachusetts, has announced his second bid for the US presidential elections as a Republican candidate.

Romney offered a scathing critique of president Barack Obama as he made his intention to run for the White House official on Thursday.

"Obama has failed America" and "the country we live in is in peril", Romney said in a speech delivered during a farm visit in the state of New Hampshire.

Romney's first priority will be improving the ailing US economy by making America the world's top job creator, he said, pitching himself as the best alternative to Obama, who has "made the recession worse".

Romney began his bid with Thursday's speech in a state crucial to his campaign. He came in second place there during his 2008 bid and has since invested heavily in it.

Possible hurdles

But Romney has a number of obstacles to overcome before winning the party nomination, Al Jazeera's John Terrett said.

"Chief among them, is that he has done this once before ... and didn't get too far," Terrett reported from Stratham, New Hampshire.

A second hurdle is the health care reforms he passed during his tenure as Massachusetts governor, our correspondent said.

"[Romney] passed health care reforms that many even in the Republican party think is suspiciously like the Obama health care reform that was pushed [recently]," he said.

"He and the party are trying to overturn the Obama health care reforms and get a lot of people to say that what Obama did was to base it all on what Mitt Romney did, when he was governor of Massachusetts."

Other challenges include his religion - Mormonism, which poses serious social problems for the party and the fact that Romney is not the only candidate bidding for the nomination, our correspondent said.

Meanwhile, Newt Gingrich, former speaker of the US House of Representatives, is set to join the presidential race, as well as congressman Ron Paul, who is popular with the ultraconservative tea party movement.

Tim Pawlenty, former governor of Minnesota, is also running and Sarah Palin - though she has not officially declared her candidacy - is another player.

But Obama has seen a soar in his approval ratings, hitting its highest point in two years - 60 per cent - after the May killing of al-Qaeda leader Osama bin Laden in Abbottabad, Pakistan.

Source: Al Jazeera and agencies