LOS ANGELES - Restaurants will be urged to voluntarily phase out trans fats from kitchens over the next 18 months under a plan unveiled by city and county leaders Tuesday.

Incentives for restaurant owners could include an official window decal indicating they have eliminated the artery-clogging substance. The decals would likely be handed out during inspections.

The decal "could help consumers decide if they want to go into a restaurant," said Dr. Jonathan Fielding, director of public health for Los Angeles County. "Restaurants want to do the right thing."

The county Board of Supervisors and the City Council backed the health effort.

Local officials were dealt a setback last week when their legal advisers said state law wouldn't allow a local ban on trans fat. The lawyers also said officials wouldn't be able to force restaurants to display nutritional information on their menus, as they had wanted. Both matters are under state jurisdiction, according to the legal opinion.

Studies have shown trans fats raise bad cholesterol and lower the good kind. Partially hydrogenated vegetable oil, the main form of artificial trans fats, is used for frying and baking and turns up in a host of processed foods: cookies, pizza dough, crackers and pre-made blends like pancake mix.

The voluntary plan is supported by restaurants, said Andrew Casana, spokesman for the California Restaurant Association.

"I haven't received one call from a restaurant saying it doesn't want to make a change," Casana said. "I get more phone calls a day from restaurants that say they've never used it."

Charlotte Austin-Jordan, who runs an M&Ms Soul Food near downtown, said her restaurant eliminated trans fat four years ago.

"It's a health issue that restaurants can't ignore," she said.

Last month, New York became the first city in the country to ban all restaurants from using artificial trans fats by mid-2008; similar measures are being discussed in cities nationwide.

Some food sellers stopped using trans fats voluntarily after the Food and Drug Administration required food labels to show trans-fat content. Wendy's International Inc. introduced a zero-trans fat oil in August. Yum Brands Inc.'s KFC and Taco Bell said they also will cut the trans fats from many foods in their kitchens.

Coffeehouse giant Starbucks Corp. recently announced it was halfway through a plan to purge trans fats from its U.S. food menu. And McDonald's said Monday it has selected a new trans-fat-free oil for cooking its french fries.