NORTH BEND, Wash. — John McCain yesterday cast Democratic rivals Barack Obama and Hillary Rodham Clinton as latecomers to the environmental battle, saying he would be willing to debate the issue with either of them in the general election to underscore his experience with the issue.

"People will trust my stewardship not only because of my background and knowledge, but also my vision for the future," he said during a news conference at a nature center in the foothills of the Cascade Mountains.

"They have never, to my knowledge, been involved in legislation nor hearings nor engagement on this issue."

McCain cited his travels to global warming hotspots, as well as his work in his home state of Arizona with Native Americans, who control broad swaths of property. He also said the Democrats' plan to auction greenhouse gas emission permits — rather than giving them away, as he proposes — would lead to higher prices for consumers.

"My proposal is doable," said McCain. On Monday, he had sketched out his action plan for global warming.

"You can dictate a lot of things, but you have to unleash the innovative power and entrepreneurship of America in order to achieve these goals," he said.

In another nod to the cause, McCain's campaign office announced it was selling eco-friendly T-shirts and polo shirts made from biodegradable fabric, as well as organic cotton hats and shopping bags.

McCain proposes to cut greenhouse gas emissions 60 percent below 1990 levels by 2050. Obama and Clinton have committed to an 80 percent cut in emissions by 2050, a level favored by many scientists.

"While Barack Obama has brought Republicans and Democrats together around plans to raise our fuel standards and invest in renewable energy, John McCain's 'long history' involves opposing countless measures to invest in renewable fuels and alternative energy technology," said Obama spokesman Hari Sevugan.

Clinton spokesman Phil Singer said: "Sen. McCain is welcome to rewrite history if he likes, but the reality is that Senator Clinton has been very active on the issue of climate change. She's even traveled with Sen. McCain a few times on trips that dealt with the issue."