Presidential candidate Mitt Romney, in danger of losing his 2012 Republican primary front-runner status, on Wednesday he would not place restrictions on carbon emissions if elected.

Romney, the former Massachusetts governor, also said he does not know if human activity is the primary cause of climate change and does not favor spending heavily on climate solutions.

Asked about global warming at a town hall meeting in Lebanon, New Hampshire, Romney said he believed the world is getting hotter and humans contribute in some way to the change -- but could not judge to what extent.

Do I think the world's getting hotter? Yeah, I don't know that but I think that it is, he said. I don't know if it's mostly caused by humans.

What I'm not willing to do is spend trillions of dollars on something I don't know the answer to.

In June, a day after launching his second bid for the White House, Romney caused a stir by saying he thought humans had contributed to climate change to some extent.

At that time he made a call for a reduction of emissions of pollutants and greenhouse gases that might be significant contributors to climate change -- a suggestion that was not made on Wednesday.

A Romney aide said the candidate has not altered his position on climate change.

A study by the National Academy of Sciences in 2010 found that climate change is occurring, is caused largely by human activities and poses significant risks. That view is backed by most climate scientists. But surveys have shown that many Republicans do not agree -- especially those who are more likely to vote in the primary elections.

Two polls on Wednesday showed Romney, a narrow front-runner in the Republican field for much of the year, has lost the lead in the Republican nominating contest, trailing Rick Perry by double digits. The Texas governor recently jumped into the race.

Campaigning in New Hampshire last week, Perry, who is typically more of a social conservative, called climate change a theory that still has not been proven and labeled the science behind it politicized.

Romney also said on Wednesday that he would make weaning the United States from imported energy from the Middle East a priority over reducing carbon emissions.

Still, using additional domestic nuclear, natural gas, and other resources could have a side benefit of cutting carbon emissions, Romney said. My view is pursue a strategy which gets us into energy independence which has as a byproduct it gets us into less CO2 emitting.

He criticized a bill backed by President Barack Obama that would have capped carbon emissions and allowed polluters to buy and sell rights to emit carbon.

I do not believe in cap and trade and I do not believe in putting a carbon cap on polluting industries, Romney said.