AMES, Iowa -- Democratic presidential candidate Hillary Rodham Clinton planned to unveil a plan Sunday aimed at combating climate change that includes revisions in the tax code to promote renewable energy.

In Iowa, the nation's second-leading wind energy producer, Clinton said people are "just not paying attention" if they don't acknowledge climate change.

Clinton said she supported renewing the wind energy tax credit and getting other tax incentives "fixed" to promote renewable fuel.

Though Clinton hinted that under her plan the coal industry would face changes, she said the federal government would help the industry.

Climate change has become a key issue in the Democratic presidential primary, where Clinton is the heavy favourite.

Changes in the tax code aimed at promoting renewable energy and transitioning away from coal is a tricky political position in key places in the country. Southeast Ohio and western Pennsylvania, states that have been pivotal in recent elections, remain the home of key coal-producing areas.

Sen. Bernie Sanders, a Democratic candidate for president to the left of Clinton who has been attracting increasingly larger crowds, told voters Sunday in Louisiana, where a gunman opened fire in a movie theatre Thursday night, that common ground can be found on gun control.

"Coming from a rural state, I think I can communicate with folks coming from urban states where guns mean different things than they do in Vermont where it's used for hunting," Sanders said. "That's where we've got to go. We don't have to argue with each other and yell at each other. We need a common sense solution."

Sanders said Americans must find common ground on gun laws, such as improved background checks to prevent gun sales to people with criminal records or a history of mental instability or domestic abuse.

He capped a weekend of Louisiana events with a rally in a suburban New Orleans convention hall that drew more than a thousand people.

Former Maryland Gov. Martin O'Malley, also seeking the 2016 Democratic presidential nomination, noted Sunday that he unveiled a climate change plan in Iowa. Campaign aides to O'Malley said that as governor, he made climate change a top priority, doubled Maryland's renewable fuel production, and reduced greenhouse gases by 10 per cent during his two terms.