"What I've said is my top priority is making sure people are able to get enough to eat. If it turns out we need to make changes in our ethanol policy to help people get something to eat, that has got to be the step we take," said Obama, D-Ill., on NBC's "Meet the Press."
"We have rising food prices around the United States. In other countries, we're seeing riots because of the lack of food supply, so this is something we're going to have to deal with," he said.
Last week, a group of Republican senators including McCain, R-Ariz., asked the Environmental Protection Agency to loosen congressional mandates to blend more ethanol and other renewable fuels into the gasoline supply, saying they are adding significantly to food costs. The mandates are backed by President Bush and senators representing farm states.
Sen. Hillary Rodham Clinton, D-N.Y., speaking on ABC's "This Week," agreed the issue needs closer review.
"What we need to do is accelerate the research into farm waste and into other cellulosic plant materials. Because, I think, instead of using the corn, let's figure out if we can use the corn cob," she said. "Let's figure out if we can use the corn stalk. Let's figure out what other kind of food, you know, waste we can use."
Clinton added: "In the short run, we've got to work with our farmers and with like-minded people around the world to figure out how this increasing use in biofuels, which is part of our answer to our dependence on foreign oil, does not undermine food production and really accelerate the prices."
Some top international food scientists last month recommended halting the use of food-based biofuels, such as ethanol, saying it would cut corn prices by 20 percent during a world food crisis.
Corn production in Wisconsin is already expected to dip slightly from last year. Wisconsin farmers said they plan to plant 3.65 million acres of corn this year, down 10 percent from 2007 but the same amount planted in 2006.
Matt Hartwig, a spokesman for the Renewable Fuels Association, has said the ethanol industry is exploring many other possible ethanol feedstocks, including wood chips, switchgrass, citrus waste and garbage.