By David Shepardson

WASHINGTON (Reuters) -U.S. auto safety regulators said Tuesday that 52 million air bag inflators produced by auto suppliers ARC Automotive and Delphi Automotive need to be recalled because they may rupture and send dangerous metal fragments flying.

The National Highway Traffic Safety Administration (NHTSA) first demanded the recall in May, but ARC rejected it. The agency issued an initial decision on Tuesday and set a public meeting for Oct. 5.

The inflators that the NHTSA is seeking to have recalled have been used in vehicles from 2000 through early 2018 produced by 12 automakers, including General Motors, Ford Motor, Stellantis, Tesla, Toyota Motor and Volkswagen.

"Air bag inflators that rupture when commanded to deploy are plainly defective, as they both fail to protect vehicle occupants as they should, and, themselves, pose an unreasonable risk of serious injury or death," the NHTSA said.

ARC in May rejected the NHTSA's tentative conclusion that a defect exists. ARC did not immediately respond to a request for comment on Tuesday.

The NHTSA said it is aware of seven confirmed inflator ruptures in the United States in the vehicles it seeks to have recalled, including seven injuries and one death.

Initially, the NHTSA said 67 million air bag inflators were unsafe, but on Tuesday it corrected that estimate to account for "over-inclusive responses reported to the agency by certain manufacturers over the course of the investigation."

GM in May agreed to recall nearly 1 million vehicles with ARC air bag inflators after a rupture in March resulted in facial injuries to a driver.

Delphi Automotive, acquired by Autoliv, manufactured approximately 11 million of the inflators under a licensing agreement with ARC, which manufactured the remaining 41 million inflators.

The NHTSA has been scrutinizing air bag inflator ruptures for more than 15 years.

(Reporting by David Shepardson; editing by Jonathan Oatis and Leslie Adler)