FILE PHOTO: A robot prepares to install the windshield to a 2019 Jeep Wrangler at the Chrysler Jeep Assembly plant in Toledo, Ohio, U.S., November 16, 2018. REUTERS/Rebecca Cook/File Photo

WASHINGTON (Reuters) - The U.S. National Highway Traffic Safety Administration said on Wednesday it was dropping a 2012 proposal to harmonize U.S. vehicle window safety standards with international rules.

Under the Obama administration, the auto safety agency known as NHTSA proposed adopting international rules on glazing materials agreed to by a world forum in 2004.

But NHTSA said it was now withdrawing the proposal because it could not conclude that harmonizing the rules “would increase safety.”

The agency cited crash data that suggests “current glazing materials are performing acceptably.” The rules were previously adopted by the European Union.

The United States already has performance requirements in place for car windows to reduce injuries resulting from impact, ensure transparency for driver visibility, and to minimize the possibility of occupants being thrown through windows in collisions.

NHTSA said safety issues around glazing had been substantially reduced since the 1960s, adding that it still planned to conduct additional glazing research.

In 2012, NHTSA said adopting the international rules would modernize U.S. testing to account for “tempered glass, laminated glass, and glass-plastic glazing used in front and rear windshields and side windows” and would “better reflect real world conditions and eliminate redundant and unnecessary testing.”

The Alliance of Automobile Manufacturers, a trade group that represents major automakers including General Motors Co, Ford Motor Co, Toyota Motor Corp and Volkswagen AG, said in August 2012 it supported NHTSA’s efforts to harmonize regulations.

“Differences, even small ones, in functionally equivalent regulations cause redundancy that adds cost to the product without benefit for the consumer,” the group wrote.