Shelby Township (US): Republican presidential candidate Mitt Romney is wading into the social and religious issues that helped fuel the rise of his rival Rick Santorum, who has excited the Republican base with his conservative social stances.

Romney, a Mormon and multimillionaire venture capitalist who served as governor of Massachusetts, took potshots at President Barack Obama on Tuesday saying his administration has "fought against religion" and sought to substitute a "secular" agenda for one grounded in faith.

His remarks contrasted sharply from his even-tempered emphasis on jobs, the economy and his resume as a can-do corporate executive, and came a day before he was scheduled to debate his Republican opponents in Arizona. He is facing a tough challenge from Santorum, who has risen in the polls with his strong anti-abortion and anti-gay marriage rhetoric, and appeals to blue-collar voters.

Romney, Santorum, former speaker of the House of Representatives Newt Gingrich and Texas Rep. Ron Paul are competing for their party's nomination to challenge Obama in the general election early in November.

Santorum surged past Romney in recent opinion polls of Republican voters after winning contests in Minnesota, Colorado and Missouri on February 7. Several polls have shown Santorum leading in Romney's native state of Michigan, where his father served as governor.

The primaries in Michigan and Arizona on Feb. 28 are next in the state-by-state contests to choose delegates to the party's national convention in August in Florida, where the Republican presidential candidate will be nominated. Romney was campaigning in Michigan on Tuesday, and was asked during a town hall meeting about how he would protect religious liberty.

"Unfortunately, possibly because of the people the president hangs around with, and their agenda, their secular agenda, they have fought against religion," he said. Obama's campaign seized on the characterisation, calling Romney's comments "disgraceful."

Religious liberty has been a leading topic in recent weeks because of the Obama administration's mandate that insurance companies provide free birth control even to people employed by church-affiliated organisations, including schools and hospitals. Opponents frame the debate as one of religious liberty while proponents of the mandate say it's about women's health and access to contraception.

(Agencies)