According to a Reuters report, a US alliance of automakers has warned that many of its members will be unable to meet a government mandate requiring a percentage of all new vehicles sold after September next year be equipped with so-called “smart” passenger-side air bags.

Reuters said that the US car industry is rushing to meet federal rules requiring sensors that detect whether a child weighing less than 25.4 kilograms (56.5 pounds) is sitting in the passenger-side front seat and turn the airbag off to prevent injury. The regulations follow the death of more than 200 people, mostly children, from airbags in the United States, Reuters added.

According to Reuters, the National Highway Transportation Safety Administration (NHTSA) has proposed that 20% of all vehicles sold by a car maker after September 2003 be equipped with the airbags, down from its original goal of 35%.

But, Reuters said, the Alliance of Automobile Manufacturers said in a letter to the NHTSA last week that many car makers would be unable to meet the regulations because of the sophisticated technology in the airbags. The alliance proposed that NHTSA cut the requirement to 10% of vehicles sold.

“Not every manufacturer can accede to a phase-in percentage greater than 10 percent,” the alliance said in a letter to NHTSA chief Jeffrey Runge, the Reuters report said.

An NHTSA spokesman told Reuters that the penalty for failing to meet the requirement is car makers must stop selling vehicles until they can reach the required volume.

Chrysler told Reuters it was still determining whether it could meet the 20% threshold. “It’s premature to give a yes-no on that,” spokeswoman Ann Smith told the news agency. “We’re still working on developing the technology.”

On the other hand, General Motors told Reuters it has already sold 112,000 model year 2003 full-size pickup trucks and sport utility vehicles with the air bags, and will have no trouble meeting the 20% threshold.

GM said it was the first manufacturer to have the smart air bags that complied with the new regulations, Reuters reported.

Reuters said GM, which had been working on the technology for a decade, decided to come to market first with a system co-developed with its former subsidiary, automotive supplier Delphi Corporation. Delphi has also agreed to supply the system to Ford and another major automaker which it declined to identify, a spokesman told Reuters.

In the GM airbag system, Reuters said, sensors under the front passenger seat measure the weight of the occupant, while other sensors detect whether the seat belt is latched and the position of the seat. The system then decides whether to turn the air bag off.

Automotive alliance spokeswoman Gloria Bergquist told Reuters her organisation also fears that the airbag sensors may not always be able to tell the difference between an adult and a child. An adult could lean forward, taking their weight off the seat and causing the airbag sensors to misclassify the passenger as a child and turn the airbag off, Reuters said.

Reuters said Ford would offer smart airbags next summer on many of its popular cars, trucks and minivans.