|Romney battled questions over his Mormon faith from evangelical voters in the 2008 campaigns [EPA]
The former governor of Massachusetts has declared his intention to run for the United States presidency in 2012, a week after Barack Obama announced his re-election bid.
Mitt Romney, an unsuccessful Republican presidential contender in 2008, formed an exploratory committee on Monday to help raise money to challenge Obama, a Democrat.
The mulitmillionaire politician, who headed private equity firm Bain Capital, begins his campaign as a well-funded early frontrunner against Obama.
He is understood to be riding high in opinion polls against other Republicans who are likely to seek their party's nomination.
Romney said Obama's economic policies had failed because he did not understand how jobs were created in the real world.
"It is time that we put America back on a course of greatness, with a growing economy, good jobs and fiscal discipline in Washington," he said in a short video filmed on Monday in New Hampshire and posted on his new website.
Romney, who battled questions about his Mormon faith from evangelical Christian voters in the last campaign, is the second major Republican candidate to form an exploratory committee in the slow-starting 2012 race.
Former Minnesota governor Tim Pawlenty took that first formal step on March 21.
Romney hovers near the top of most polls of Republicans along with Mike Huckabee, the former Arkansas governor, who also ran for the party's 2008 presidential nomination.
Broad name recognition
Romney boasts broad name recognition, extensive fundraising contacts and wherewithal that likely will make him the early favourite in a Republican field still waiting to take shape.
Other possible well-known contenders like Huckabee and Sarah Palin, the former Alaska governor, may not enter the race at all.
But Romney, 64, has been planning his run since he lost the 2008 presidential nomination to John McCain, the Arizona senator, traversing the country frequently to speak to potential supporters and to court donors.
"He's the guy at this point who everyone has to chase after," Republican consultant Rich Galen said.
"Given the current state of the field, Romney has to be considered the fron-runner."
Romney has already faced criticism from conservatives for his support as governor of a broad healthcare programme in Massachusetts that became a model for the national healthcare overhaul pushed and signed into law by Obama.
Democrats were holding events on Monday in Massachusetts and elsewhere to celebrate and highlight the fifth anniversary of the Massachusetts healthcare law when Romney made his announcement.
With the health of the US economy and unemployment - which hovers at just below nine per cent - likely to dominate the campaign for 2012 race, Romney stressed his business experience in his announcement.
"My work led me to become deeply involved in helping other businesses, from innovative startups to large companies going through tough times," Romney said.
"Sometimes I was successful and helped create jobs, other times I was not. I learned how America competes with companies in other countries, why jobs leave, and how jobs are created here at home."