At the museum, Bush toured exhibits of fuel cell technology - pointing a hydrogen-powered television camera at reporters, making a phone call on a fuel-cell mobile phone, and inspecting a lineup of fuel-cell vehicles.

Outside, a small group of demonstrators carried signs protesting his energy policies and handed out leaflets denouncing the fuel cell proposal as a "dirty energy plan," because part of the plan would seek ways to produce hydrogen using coal and nuclear power.

"The whole thing's a fraud," said Dan Becker, head of the Sierra Club global warming and energy program. "He's going to try to snatch defeat from the jaws of victory by creating hydrogen out of coal, nuclear and gasoline."

He said the plan obscured Bush's failure to seek stronger fuel-efficiency standards for today's cars and trucks, which would provide quicker energy savings.

Democrats gearing up to seek the 2004 presidential nomination also took shots at the plan, which could give Bush an environmental plank for his reelection campaign.

Sen. John Kerry of Massachusetts called the plan a "smokescreen on energy security" and Sen. Joseph Lieberman of Connecticut said it was "nothing more than an exhaust pipe dream."

Bush unveiled his hydrogen fuel initiative last week in his State of the Union speech, proposing $1.2 billion overall and new spending of $720 million over five years to develop technology and infrastructure to produce, store and distribute hydrogen for use in fuel cells and electricity generation.

A separate program previously launched to develop fuel cell vehicles raises the five-year spending total to $1.7 billion.

Fuel cells produce electricity from oxygen and hydrogen. The hydrogen to power them can be obtained from water, natural gas, coal or other resources, and the fuel cells emit only water as a byproduct.

White House spokeswoman Claire Buchan said the research on using coal to produce hydrogen would seek ways to make it "cleanly."

A White House fact sheet said the proposal would lead to cost-effective fuel-cell vehicles by 2020.

"I don't know if you and I are going to be driving one of these cars, but our grandkids will," Bush said.

He said fuel-cell cars would not only cut air pollution, they would reduce U.S. dependence on imported oil, enhancing the country's economic security. "If we develop hydrogen power to its full potential, we can reduce our demand for oil by over 11 million barrels per day by the year 2040," he said.

The United States currently uses about 20 million barrels daily, half of which is imported.