The Chrysler vehicles, from model years 2003-2007, are among an estimated 4.2 million involved in a series of regional recalls in high-humidity regions announced in June by the National Highway Traffic Safety Administration.

Chrysler, a unit of Fiat Chrysler Automobiles, said in documents filed with NHTSA that Takata "has made no determination of a safety defect" in the inflators being studied by the safety agency, but it would nonetheless begin replacing them no later than Dec. 19.

It could start the recall in parts of Florida in early December, according to the NHTSA documents.

The Chrysler vehicles include the Dodge Ram, Durango, Dakota, Charger and Magnum, and Chrysler Aspen and 300.

Takata was not immediately available for comment.

The group of Takata inflators the NHTSA is studying - the so-called Beta series - totals 37.8 million, according to NHTSA documents. Of those, about 25 million are passenger-side inflators made from 2000-2004 and about 12.8 million are driver-side inflators made from 2004-2007.

Other manufacturers involved in the June regional recalls include Honda Motor Co, Toyota Motor Corp, Nissan Motor Co, Mazda Motor Corp, Ford Motor Co, General Motors Co, BMW AG, Mitsubishi Motors Corp and Fuji Heavy Industries' Subaru.

Takata's air bag inflators are being investigated because, if exposed to moisture or improperly manufactured, they can explode, rupturing and sending metal shards into vehicle passenger compartments. The issue has been linked to four deaths and 160 injuries.

Since 2008, more than 11 million U.S. cars equipped with Takata air bags have been recalled because of the inflator issue.

Chrysler told NHTSA that it conducted a joint investigation with Takata of the Beta inflators, including samples obtained from Florida junkyards.

Takata's analysis showed the Florida inflators "exhibited slightly elevated levels of moisture," Chrysler said.

The automaker said Takata has been conducting a series of tests on suspect inflators, including CT scans, "live dissections" and live deployments, while measuring performance, moisture level and other physical and chemical properties.

(Reporting by Paul Lienert and Ben Klayman in Detroit; Editing by Alan Crosby)

By Ben Klayman and Paul Lienert