New York City's 24,000 restaurants started showing their grades on Wednesday - A, B, or C - under a new system of ranking sanitary conditions by the city's health department.

The new system is aimed at increasing public awareness of health in food preparation and encouraging better practices in food establishments.

Health Commissioner Thomas Farley awarded the first A grade to the tiny Sparks Deli in Queens.

"Sparks has set an example," Mr Farley said.

"Whether it's a neighbourhood deli or a pricey dinner house, any food establishment can prepare food safely."

The restaurants will be required to display their health grades publicly and a city website will allow users to determine an individual restaurant grade.

"Most restaurants maintain good conditions, but lapses in food safety cause a lot of preventable illness in New York City," Mr Farley said.

"Food-borne illness prompts thousands of hospital visits each year, and it costs many New Yorkers valuable days off work or school.

"By putting information about inspection results on public display, we give diners the information they want while also encouraging restaurants to improve their food preparation practices."

Under the system, restaurants with A grades will be inspected annually, while those receiving lower marks will get more frequent visits.

Restaurants with code violations will get a chance to improve their scores on a reinspection.