The question of how quickly to introduce the country to hydrogen technology arose at the National Hydrogen Association's 17th annual meeting, held last week in Long Beach, Calif. The 1,100 attendees included a contingent from Air Products and Chemicals Inc. of Trexlertown, the world's largest hydrogen supplier.

Hydrogen, an abundant element, can be used to make low-pollution or pollution-free electricity to power cars, buildings and more. Backers say hydrogen could help wean America off dirty, imported fossil fuels — but not for 20 years or more, as scientists tackle major technical and supply challenges.

Some in the hydrogen field have been wary of pushing it too far into the public eye. They fear that rushing the technology into everyday use could backfire.

But utility industry veteran S. David Freeman used his speech at the association's awards luncheon Tuesday to try to jostle the industry into faster action.

High oil prices, continued pollution problems and other factors give hydrogen an immediate opportunity to score points with America, Freeman said. And, while the fuel is not ready for a full-scale rollout, some uses — including certain types of hydrogen-powered cars — are far enough along to be displayed and promoted on a limited basis, he said.

''I don't understand why we're not bragging about what we can offer today,'' said Freeman, president of the Los Angeles Board of Harbor Commissioners. ''I don't understand why there's a reluctance.''

To some degree, President Bush set the cautious tone in his 2003 State of the Union address, when he predicted an American child born that year would grow up to drive a hydrogen car. Freeman said the industry needs to shoot for more immediate gains, though.

''Saying, 'This is for the grandchildren,' is not a very good marketing approach,'' he said.

It remains to be seen whether the industry will take Freeman's advice. Some at the conference said the two outlooks can be balanced. Steve Ellis, manager of fuel cell marketing for Honda, compared the situation to a marathon, in which racers run long and steady but are capable of bursts of speed.

''Let's all maintain a reasonable pace so we make it to the finish line,'' Ellis said at a Wednesday morning forum.

The weeklong meeting included one significant reach out to the public. Some 400 people who were not part of the conference showed up at a ''ride and drive'' event Tuesday. They took turns driving nine hydrogen-powered cars over part of the route of the Toyota Grand Prix of Long Beach auto race.

Many hydrogen-powered cars use fuel cells, devices that turn hydrogen into electricity using chemical reactions. Fuel cells' range and reliability cannot yet match those of gasoline engines. They also use costly precious metals to trigger the reactions, making them too expensive for routine production.

One recurring theme of the conference was the increasing use of internal-combustion engines, such as those in today's cars, converted to run on hydrogen. Those engines are not as clean as fuel cells. But they are cheaper, more reliable, can be made on the same assembly lines as gasoline engines, and can serve as a ''bridge'' technology until fuel cells improve.

''I think internal combustion engines are going to have to play a very important role in the transition to the ultimate fuel cell vehicle,'' said Venki Raman, an independent industry consultant from Emmaus.

Freeman, in keeping with his theme, called for carmakers to increase their production, and promotion, of hydrogen internal-combustion engines.

''It seems [hydrogen combustion engines] are almost a military secret. It's all fuel cells, fuel cells, fuel cells,'' he said.

Building a hydrogen fueling network, a common topic whenever hydrogen researchers gather, also emerged as a subject of debate — and disagreement.

For hydrogen cars to work on a large scale, energy companies need to build hydrogen pumping stations. The stations might make hydrogen on-site, have it piped in from nearby plants, or get it trucked in by trailers. Regardless of method, the hydrogen network is expected to cost billions of dollars to build.

The hydrogen network is often framed as a high-stakes chicken-and-egg scenario. Automakers don't want to build large numbers of hydrogen cars without fueling stations in place to serve them. And energy companies don't want to build the stations, which can cost $1 million each, without enough cars to make them viable.