US auto safety regulators said on Wednesday there were about 85 million unrecalled Takata Corp air bag inflators in US vehicles that would eventually need to be recalled unless the company can prove they are safe.

This is the first public accounting by the US government of the total number of unrecalled Takata air bag inflators. So far 28.8 million in the US have been recalled due to the risk that they can explode with too much force and spray metal shards inside vehicles.

More than 11 people have been killed worldwide in incidents linked to defective Takata inflators, including the March 31 death of a 17-year-old driver in Texas. Globally, more than 50 million have been recalled.

Further recalls would add to already hefty estimated bills for the Japanese parts maker.

Analysts have estimated that if Takata is found to be solely responsible for the fault in the inflators, now the subject of several industry investigations, it could face a bill of more than $3.5 billion for inflators recalled to date.

Takata declined to comment on the issue on Thursday.

Under an agreement signed last year, the company has until 2019 to demonstrate that all of its unrecalled air bag inflators are safe.

The prospect of ballooning recall costs has prompted Takata to look for a financial backer and it plans to draw up a list of candidates by August, two people familiar with the matter said on Tuesday.

The parts maker has been widely criticised for dragging its feet in identifying air bag inflators that needed to be recalled, and for providing incomplete and inaccurate data to transport authorities and automaker customers.

A Tokyo-based spokesman for Honda Motor Co, which so far has recalled the largest number of vehicles over the issue, said that the automaker would cooperate with authorities to take swift and appropriate action if additional recalls are announced.

The NHTSA said on Wednesday that potentially defective Takata air bags still on the road include 43.4 million passenger side inflators, 26.9 million side air bag inflators and 14.5 million driver side inflators.

Japanese transport authorities said they did not have equivalent estimates for unrecalled Takata air bag inflators globally or in Japan, where 12 million have been recalled to date.

Honda, Toyota Motor Corp and other automakers have said they will stop using Takata air bag inflators in new models. Some have also been sourcing replacement inflators from alternative suppliers. - Reuters