SOMERSET, Pa. - Former senator Rick Santorum confirmed Monday that he is running for president, joining a crowded field of Republicans looking to challenge President Barack Obama in next year's election.

Santorum, the former No. 3 Republican in the U.S. Senate and a favourite among his party's anti-abortion rights bloc, is a long shot for his party's nomination. He announced his candidacy Monday morning on ABC television. The announcment had been expected for months.

"We're in it to win it," he said, appearing in front of a banner-draped setting in Somerset, Pennsylvania, where he will make the formal announcement later Monday. Santorum used his brief TV appearance to criticize Obama's foreign policy, saying among other things he believes Obama has gone too easy on Iran, which is suspected of trying to obtain nuclear weapons.

Other Republican contenders include former Massachusetts Gov. Mitt Romney, former House Speaker Newt Gingrich, U.S. Rep. Ron Paul, and former Utah Gov. Jon Huntsman, who also served as U.S. ambassador to China. Those considering a bid include Texas Gov. Rick Perry and Congresswoman Michele Bachmann. The party's 2008 vice-presidential nominee, Sarah Palin, hasn't said whether she would run.

Santorum, a blunt-talking conservative, lacks the name recognition and fundraising organization of his better-known rivals. But the two-term senator's advisers are counting on social conservatives who have huge sway in some early nominating states and have yet to settle on a favourite candidate.

He had been laying the groundwork for a presidential bid when he lost a bruising re-election bid to the Senate in 2006. His opposition to abortion, gay marriage and embryonic stem cell research makes him an appealing candidate for conservatives. But his sometimes abrasive style alienated voters in Democratic-leaning Pennsylvania, and they replaced him with Bob Casey, an anti-abortion Democrat.

Santorum's policy positions align with national conservatives who now are looking at many of the expected candidates with skepticism. Romney's changes of heart on gay rights and abortion do little to help his second presidential effort, Gingrich is twice divorced. Huntsman, who worked for three Republican administrations, nonetheless accepted President Barack Obama's offer to be the U.S. ambassador to China

Santorum, 53, has his own hurdles to overcome: He has been out of elective office since 2007 and lacks the robust fundraising or personal wealth of his likely rivals.

Earlier this year, he established a presidential exploratory committee to start raising money and joined the first -- though ill-attended -- Republican presidential debate in South Carolina. He is expected at next Monday's debate in New Hampshire, which is likely to include more of the expected field.