"This is our generation's moment to save future generations from global catastrophe by creating a market for clean-burning fuels that can stop the dangerous transformation of our climate," Obama said in prepared remarks.

"In states like New Hampshire and California, people are taking the lead on producing fuels that use less carbon," he said.

The Illinois senator planned to offer his energy proposal today at the University of New Hampshire. The approach echoes California's.

California's Republican governor, Arnold Schwarzenegger, issued an executive order this year saying that all fuels in the state contain lower carbon content. The goal is to reduce carbon intensity of California's passenger vehicle fuels by 10 percent by 2020.

The Obama campaign said its effort would take that plan nationally. Specifically, Obama wants to cut greenhouse gas emissions from cars by 5 percent in 2015 and 10 percent in 2020.

"It will take a grass-roots effort to make America greener and end the tyranny of oil," Obama said. Earth Day this Sunday, he said, "should mark the beginning of a nationwide effort to harness our technology, our ingenuity and our will to achieve energy independence in our time."

Obama's plan counts on new limits to force increased production of renewable biofuels, such as corn and cellulosic ethanol, which naturally have lower emissions. The plan would create incentives for increased research, investment in cleaner fuels and flexible-fuel vehicles that can run on ethanol.

The campaign says a national fuel standard would reduce greenhouse gas emissions by about 200 million tons in 2020 compared with 2007 levels — the equivalent of taking about 32 million cars off the road in 2020. The campaign also estimates the annual consumption of gasoline derived from foreign oil imports would drop by about 30 billion gallons in 2020.