A federal plan to raise the corporate average fuel economy (CAFE) standard for light trucks by 1.5 mpg would cost General Motors Corp. $1.1 billion and lead to trucks that are lighter and less safe, the automaker told the National Highway Traffic Safety Administration (NHTSA).

GM said NHTSA overestimated the company's ability to meet the proposed fuel economy requirements and said the agency counted some technologies twice in its estimates, The Detroit News reported Wednesday.

In its filing with NHTSA, GM estimated that it would only be able to achieve 20 mpg in 2005, 20.1 mpg in 2006 and 20.8 mpg in 2007. NHTSA has proposed raising fuel economy standards for light trucks from 20.7 to 22.2 mpg in the 2007 model year.

GM said the regulations would add $1.1 billion in costs over the three-year period. NHTSA has estimated a cost of $703 million.

NHTSA announced the proposed CAFE increase December. It said it based the increase on the potential available technology without requiring automakers to sacrifice performance or reduce vehicle weight.