WASHINGTON (AFP) - United States safety regulators pushed on Tuesday for a nationwide recall of cars with defective Takata air bags, increasing the pressure on both the Japanese company and automakers ahead of a Senate hearing into the deadly problem.
An earlier recall limited to several mostly southern US states needed to be expanded to the full country, said Mr David Friedman, deputy administrator of the National Highway Traffic Safety Administration (NHTSA).
"We now know that millions of vehicles must be recalled to address defective Takata air bags and our aggressive investigation is far from over," said Mr Friedman. "We're pushing Takata and all affected manufacturers to issue the recall and to ensure the recalls capture the full scope of the problems."
The agency warned that if Takata and the manufacturers do not quickly make the recall voluntarily, it will use its powers to force one.
One month ago, the NHTSA issued a warning over 7.8 million cars in the US with the air bags.
On Tuesday it also ordered Takata - subject of a US criminal investigation into its exploding air bags - to provide documents and other detailed information on the propellant used in its air bag inflators.
"In recent days, Takata has publicly conceded that it changed the chemical mix of its air bag inflator propellant in newly designed inflators," the NHTSA said.
"As part of its ongoing investigation, the agency will analyze the information received to determine if the chemical composition of Takata's propellant mix may be a cause and/or contributing factor in the air bag inflator ruptures."
The ratcheting up of pressure on Takata comes ahead of a Senate hearing on Thursday at which top officials from Takata, Honda and Chrysler are scheduled to testify on the defect, blamed for several deaths and numerous injuries in the US and beyond.
Mr Friedman will also testify, with the agency facing growing calls to explain why recalls so far have been limited to only several US states.
In contrast, about 16 million cars worldwide from 10 automakers have been recalled over the defect.
Last month, in its initial warning, the NHTSA said that motorists in warm-weather US states should take "urgent" action because the air bags were thought to have a greater risk of rupturing in cars operated in areas with high humidity.
In Tuesday's statement, the agency stuck by its view that cars in warm, humid climates are most likely to suffer the problem.
"While NHTSA is not aware of either field incidents or test data suggesting that the problem affecting passenger-side air bags in the areas of persistently high humidity extends beyond those areas, the agency has been pushing the industry to perform testing to ensure that current recalls effectively cover vehicles with air bags that could be potentially affected by this defect," it said.