A top Toyota Motor Corp (7203.T) executive said on Wednesday the Japanese automaker has no plans to abandon Takata Corp (7312.T) despite the supplier's struggles with air bag inflators that could rupture and spray metal shrapnel at vehicle occupants.

U.S. safety regulators on Wednesday expanded the number of vehicles in the United States affected by recalls for this problem by 28 percent to 7.8 million vehicles.

Toyota has the second largest number of vehicles affected by the U.S. recalls at 877,000, trailing only Honda Motor Co's (7267.T) 5.1 million vehicles, according to the U.S. National Highway Traffic Safety Administration (NHTSA).

Steve St. Angelo, head of Toyota's Latin American operations, appearing at an event in Tokyo, said Toyota was standing by Takata, when asked whether the Japanese automaker had ever dropped a supplier.

"Toyota, when you become one of our suppliers, you really become part of our family," he told reporters. "Toyota is very big on helping a supplier, on struggle points.

"Toyota's not one to just dump a supplier," he added. "Have we ever eliminated a supplier? Yes. But it's really, really tough. We will exhaust every opportunity to help that supplier first."

St. Angelo, the company's former chief quality officer in North America, said Takata was "doing what they're supposed to do: understand the root cause, and then learn from it ... and put countermeasures in place."

NHTSA is investigating whether Takata air bag inflators made between 2000 and 2007 were improperly sealed. Bags inflating with too much force have the potential to spray metal shrapnel at occupants. They have been linked to four deaths and resulted in several lawsuits.

The probe has focused on inflators recovered from cars being recalled for repairs in hot and humid places like Florida. Takata is cooperating with that investigation along with 10 automakers.

More than 16 million vehicles globally have been recalled because of defective Takata air bags since 2008.

Takata's largest customer, Honda, has already moved some business to rival inflator maker Daicel Corp (4202.T), a person with knowledge of the matter has said. Honda Executive Vice President Tetsuo Iwamura said in July the automaker was reviewing whether to keep buying from Takata.

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