WASHINGTON » Japan’s Takata Corp. rejected U.S. regulators’ demand Wednesday for an expanded, nationwide recall of millions of air bags, setting up a possible legal showdown and leaving some drivers to wonder about the safety of their cars.

Amid the standoff, Honda Motor Co. decided to act on its own and recall cars with the potentially defective equipment in all 50 states. But other automakers have yet to make a decision.

At issue are air bags whose inflators can explode with too much force, hurling shrapnel into the passenger compartment. At least five deaths and dozens of injuries have been linked to the problem worldwide.

During the past six years, Takata and 10 automakers issued a series of recalls covering 8 million cars in the United States, mostly in high-humidity areas such as the Gulf Coast and Hawaii, because of evidence that moisture can cause the propellant to burn too quickly. But after incidents in California and North Carolina, the National Highway Traffic Safety Administration began pressing for the recall of 8 million more vehicles from coast to coast — a demand that Takata flatly rejected.

"There’s not enough scientific evidence to change from a regional recall to a national recall," Hiroshi Shimizu, Takata senior vice president of global quality assurance, told a House subcommittee on Capitol Hill.

Takata also contends that NHTSA has authority to seek recalls only from auto manufacturers and makers of replacement parts, not from original parts suppliers — a position NHTSA contests.

Shimizu insisted that the air bags are safe: "I would drive a car with a Takata air bag."

David Friedman, NHTSA deputy administrator, said he was "deeply disappointed" by Takata’s response.

The agency is now gathering proof that a recall is needed, which it will present at a public hearing. After that, NHTSA could order Takata to undertake a recall, and take the company to court if it refuses. But Friedman acknowledged that could take months.

"It’s time for industry to step up," Friedman told lawmakers. "Until (Takata) and automakers act, affected drivers won’t be protected."

The stalemate is likely to add to the confusion among car owners, many of whom are already bewildered because some of the recalls have covered driver’s-side air bags, while others applied to passenger-side air bags, and a few covered both. The NHTSA-demanded recalls would involve driver’s-side air bags.

At Wednesday’s hearing, Rep. Jan Schakowsky of Illinois, the panel’s senior Democrat, said she has received letters from constituents "who are literally afraid to drive their cars."

Rep. Billy Long, R-Mo., warned that driving a car with a Takata air bag is "tantamount to driving down the highway with a shotgun pointed at you."

Drivers whose cars have been recalled should have received notices in the mail. A driver can also key in the vehicle’s identification number at www.safercar.gov or call the dealer to see whether the car is covered.

But for those outside the recall zone who want to know whether their air bags are safe, things get trickier. It’s difficult to tell whether a car has a Takata air bag inflator; car owners can try asking their dealer, but even they may not know.

Honda is Takata’s largest customer, but the company also made air bags for Ford, Chrysler, Mazda and BMW. Mazda said Wednesday that it will probably expand its recall, while BMW said it is evaluating the situation.

Ford and Chrysler both expanded passenger air bag recalls Wednesday to include states outside of the initial high-humidity zones. But neither automaker recalled additional driver’s- side air bag inflators, as Honda did.