Newt Gingrich, the latest candidate to surge to the top of the Republican presidential race, said the United States and its allies could "break Iran in a year" as he and his rivals looked to use a debate Tuesday night to boost their foreign policy and national security credentials.

Gingrich, speaker of the House of Representatives in the 1990s, said that ending gasoline sales to Iran and sabotaging its refineries would lead to the collapse of the Iranian government and end its nuclear ambitions.

He said he would bomb Iran only as a last resort and with a goal of bringing about the downfall of the government.

This was the second debate in less than two weeks to focus on foreign affairs in a race otherwise dominated by domestic issues. Republicans see the weak U.S. economy as President Barack Obama's biggest vulnerability.

It came six weeks before the first nominating contest, the Iowa caucuses. Candidates were looking to use the debate to build or _ for Gingrich and fellow front-runner Mitt Romney _ sustain momentum.

The candidates sparred over how far America should go in sacrificing liberty in order to prevent terrorist attacks.

Gingrich backed the anti-terrorism law known as the Patriot Act, which was passed after the Sept. 11, 2001, attacks and has been criticized by civil libertarians. But Congressman Ron Paul warned that the law is "unpatriotic because it undermines our liberties."

Paul went against most of the other candidates with his views not only on the Patriot Act, but also in his calls to cut aid to Israel, withdraw troops from Afghanistan and decriminalize drugs. His libertarian views have won him a solid core of supporters but he has been unable to break into the top tier of the race,

Romney, the former Massachusetts governor, has led the race for most of the year, but has been unable to expand his support beyond the 25 percent level. Meanwhile, a series of rivals have surged to the top, only to fade. They include Congresswoman Michele Bachmann, Texas Gov. Rick Perry and businessman Herman Cain.

Gingrich is near the top of many polls now, but it is not clear if he can stay at the top. Beyond questions about his divorces, extramarital affairs and business dealings, his past views on climate change and other issues could be seen as too moderate for some conservatives.

Except for longshot candidate Jon Huntsman, Obama's former ambassador to China, the Republican contenders generally lack significant foreign affairs experience, so the debate offered the potential for gaffes.

Cain's candidacy has been damaged already by a rambling answer to an interviewer's question about Libya. That further set back a campaign struggling to recover from a sexual harassment scandal.

At Tuesday's debate, Cain said he would support an Israeli military strike against Iran's nuclear facilities only if he were convinced it would work.

Debates have been particularly troublesome for Perry, whose hopes for reviving his fading candidacy were damaged after a much-mocked stumble at a recent debate, when he couldn't remember the names of all three federal agencies he wanted to eliminate.

With unemployment stubbornly high and the economy sluggish to recover from recession, the candidates have been driving the foreign policy discussion back to pocketbook issues at home.

A day earlier, a bipartisan congressional panel charged with recommending measures to reduce the giant U.S. deficit declared an impasse. That could trigger deep cuts in 2013 spreading across military as well as domestic spending.

Many of the presidential candidates have called America's $15 trillion government debt a national security threat, especially because China is the single largest creditor. Obama's own defense secretary, Leon Panetta, has said big Pentagon cuts "would lead to a hollow force incapable of sustaining the missions it is assigned."