The House Energy and Commerce Committee approved legislation that would strip the Environmental Protection Agency of some of its authority but would not block a proposal to regulate heavy- and medium-duty truck greenhouse gas emissions.

Automakers may forego as much as $4 billion a year in light truck sales to prevent states led by California from setting their own mileage standards, Bloomberg reported Tuesday.

President Obama’s proposed 2012 budget for the Environmental Protection Agency would eliminate diesel emissions-reduction grants and shrink other agency programs. But EPA Administrator Lisa Jackson last week vowed to forge full-speed ahead with the agency’s greenhouse gas emissions reduction program, including the agency’s proposed truck fuel-efficiency rule.

President Obama signed the Diesel Emissions Reduction Act into law Jan. 4.

Sens. Tom Carper (D-Del.) and George Voinovich (R-Ohio) introduced a bill that would reauthorize a voluntary national and state-level grant and loan program to reduce diesel emissions.

The trucking industry reaffirmed its support of national fuel efficiency and greenhouse gas emission standards for heavy- and medium-duty trucks while testifying in Chicago Monday at the first of two federal public hearings on the subject.

American Trucking Associations said Friday it has adopted a carbon-emissions control policy supporting a national fuel-economy standard for trucks, rather than government actions to increase fuel prices or alternative-fuel mandates.

A coalition of industry groups, including American Trucking Associations, touted its own voluntary efforts toward improving environmental sustainability as part of its push toward what it called “responsible” energy policies.