Japanese automotive supplier Takata has told American senators that it may not be able to move quickly to provide replacement parts for millions of vehicles fitted with its potentially fatal airbags.

Takata's senior vice president for global quality assurance Hiroshi Shimizu told the US Senate Commerce Committee on 20 November that even if the firm steps up production of replacement kits beyond the current capacity of 300,000 units a month, it may still not have enough parts.

David Friedman, deputy administrator of the US National Highway Traffic Safety Administration (NHTSA), told the committee that his agency was in touch with two other suppliers to ascertain whether they could manufacture replacement parts.

When pressed by Republican Senator Dean Heller for Takata to take "full responsibility" for five deaths linked to the faulty airbags, Shimizu consulted a colleague multiple times, Reuters reported.

He answered that two of the five fatalities were still being probed, but acknowledged "anomalies" with Takata airbag parts involved in some fatal accidents.

Shimizu, in his prepared comments, said that Takata was "deeply sorry and anguished about each of the reported instances."

"Even if we increase [production of replacement kits] to 450,000, maybe still that's not speedy enough," he added.

Takata's stock has lost some 59% so far this year in Tokyo trade.

High Stakes

The hearing held high stakes for Takata, which supplies one in five air bags globally. The firm is facing a criminal probe into the scandal, over 20 class action lawsuits and an NHTSA probe.

On 18 November, the US highway regulator called on Takata and five other automakers to expand their regional recalls of driver-side air bags to cover the entire US, as senators have urged.

But Friedman said a parallel move to recall passenger-side airbags nationwide would risk diverting parts from regions of high humidity, where they are judged to be at highest risk.

Regulators and Takata have yet to identify why the parts are at risk. Takata believes the "root causes" of the airbag inflator ruptures are a combination of the age of the inflator, constant exposure to high humidity and problems in production.

About 16 million cars with Takata airbags have been recalled globally, with more than 10 million of those in the US and two-and-a-half million in Japan.