TOKYO -- U.S. transport authorities intend to call for automakers to recall more cars equipped with potentially defective Takata air bags, sources said on Saturday.

The U.S. National Highway Traffic Safety Administration has already conveyed its recall expansion plan to automakers, the sources said. Tens of millions of cars are expected to be affected.

Around the world, about 60 million vehicles have already been recalled over the matter.

Under the NHTSA's plan, the recall will expand to all cars with Takata air bags that use ammonium nitrate, an ingredient in gunpowder, but do not contain desiccant to prevent a part of the bag from deteriorating.

There are believed to be more than 100 million so-equipped vehicles around the world.

The NHTSA is expected to announce its recall expansion plan by the end of May. If the transport authorities of Japan and other countries follow in the footsteps of the NHTSA, more than 10 Japanese, U.S. and European automakers will be forced to report additional recalls to them.

Automakers have so far shouldered the bulk of the costs of recalling cars fitted with the Takata air bags in question. The expansion could push these costs by around 500 billion yen ($4.7 billion).

Mazda Motor on April 27 said it had booked an extraordinary loss of 40.7 billion yen related to the recall for fiscal 2015, which ended on March 31. The reserve was for "almost all" of the defective air bags, President Masamichi Kogai said.

Honda Motor has been hit particularly hard by the matter as it uses more Takata air bags in its cars than any other automaker. It has already recalled some 30 million cars globally, mostly in Japan and the U.S. The Japanese automaker is believed to have so far booked recall-related costs of around 320 billion yen.

It is thought that more than 15 million Honda cars equipped with Takata air bags that do not contain desiccant have yet to be recalled. Honda will likely face an additional recall cost of about 200 billion yen.

Toyota Motor and Nissan Motor use fewer Takata air bags than Honda. But an expansion of recalls could still cost Toyota more than 100 billion yen and Nissan several tens of billions of yen.

After all recall plans are made available, automakers and Takata will discuss how to share the costs.

(Nikkei)