SAN FRANCISCO -- San Francisco supervisors gave preliminary approval to a new city ordinance Tuesday that would require chain restaurants to begin labeling their menus with health information.

The ordinance, introduced by Supervisor Tom Ammiano, requires restaurants having at least 20 outlets in the state to display information on calories, saturated fat, carbohydrates and sodium for all menu items.

That and additional information including trans fat, protein and cholesterol would also have to be displayed in a conspicuous location near the restaurant's entrance.

However, existing requirements for disclosure of information about artificial colorings and flavoring, chemical preservatives, polyunsaturated fat, vitamins and minerals would be eliminated under the ordinance.

The program would be paid for by a $350 surcharge for city permits issued to the restaurants. First-time violators could be fined $100.

On Tuesday, Ammiano called the ordinance "an important piece of legislation" in the fight against obesity, diabetes and other nutrition-related diseases that impact individuals and families, as well as the city resources.

Similar legislation also being pursued on the state level, he said.

The ordinance was hammered out in cooperation with the Golden Gate Restaurant Association, Ammiano said, noting though that there is still some discussion on "an issue dealing with pizza."

The ordinance passed unanimously on first reading today and will come before the board for a final vote next Tuesday.