Safety advocates say the Bush administration is waging a halfhearted battle against highway deaths by letting automobile manufacturers install automatic seat belts as a substitute for air bags.

But the administration's top highway safety official says his approach will save thousands of lives each year by encouraging the use of air bags while giving the industry flexibility to develop other means of protecting motorists.Jerry R. Curry, head of the National Highway Traffic Safety Administration, on Thursday ordered automakers to begin equipping passenger trucks and vans with front-seat air bags or automatic seat belts no later than 1994.

The new rule extends to vans, light trucks, utility vehicles and small buses the same requirement that is in effect for cars.

It could prevent up to 2,000 deaths each year when fully in effect after Sept. 1, 1997, Curry said. "Today is a red-letter day in the history of highway safety," he said.

But consumer groups told a Senate subcommittee the regulation was inadequate. They supported a bill sponsored by Sen. Richard Bryan, D-Nev., that would mandate driver and front-seat passenger air bags in all new passenger vehicles by Sept. 1, 1997.

Air bags are far superior to automatic belts, many of which are poorly designed and "downright dangerous," said Benjamin Kelley of the Institute for Injury Reduction. Some automatic belts are attached to the car door and unlatch when a collision or rollover causes the door to open, he said.

Curry acknowledged that air bags are preferable to automatic belts. But he said the air bag is far less effective if the driver fails to buckle his manual seat belt.

Curry said he had no quarrel with Bryan's goal but said the bill wasn't needed because automakers are rushing to make air bags standard equipment. By the 1996 model year, 90 percent of new cars probably will have driver and passenger side air bags.

Automakers spoke against the bill.

"Setting a design standard in legislation places an unwarranted burden on the industry," said Greg Dana of the Association of International Automobile Manufacturers.