AUGUSTA (AP) - A Senate-approved bill to make nonuse of motor vehicle seat belts a primary offense was rejected Thursday by the House of Representatives, but only narrowly.

The 70-67 House vote against the measure came a week after a 20-14 vote in favor of it in the Senate, and the House outcome left supporters of the bill believing they still have a good shot at winning passage.

"I think it has a real chance still," said Rep. Boyd Marley, D-Portland. Additional voting in both chambers is still to come.

Maine's present law prohibits enforcement of the seat belt law unless the driver has been stopped for violation of another law. The bill sponsored by Sen. Christine Savage, R-Union, a Transportation Committee veteran, would change the law from a secondary to a primary offense. It would allow a police officer to detain and cite a driver or passenger 18 or older solely for failing to wear a seat belt.

Seat belts and child safety seats are now mandatory and a primary offense for persons under 18 in Maine.

Marley, the House chairman of the Transportation Committee, said the new measure had already drawn more support than in the past and that he believed there was similar momentum in other states.

Last fall, the Maine Bureau of Highway Safety reported that 77.2 percent of motorists used seat belts, the highest level since the state began surveying motorists two decades ago and a sharp increase over the 23 percent recorded during the first survey in 1986.

While seat belt use nationally is reaching record levels, highway safety officials said last year that 48 million people still were not regularly buckling up when they were on the road.

The government has been pushing for states to enact primary enforcement laws. As of last year, half of the states, the District of Columbia and Puerto Rico had adopted primary enforcement laws like the one Maine is now considering.

AP-ES-03-22-07 1416EDT