A federal appeals court said today it wants the Food and Drug Administration to weigh in on whether its rules permit cities to force restaurants to display calorie listings.

At stake is the city’s novel requirement that some chain restaurants put calorie counts on menu boards. Implementation of the rule has been delayed by a lawsuit brought on behalf of restaurants by the New York State Restaurant Association, a trade group.

A three-judge panel of the 2nd U.S. Circuit Court of Appeals delivered tough questions to lawyers for both sides in the dispute today, and one judge directed lawyers for the restaurant association to ask the FDA to issue an opinion on the subject within a month.

At one point, Judge Chester Straub taunted a senior counsel for the city law department, Fay Ng, as he asked why the city was not willing to voluntarily delay enforcement of the requirement beyond June 6, when fines will begin to be issued to violators.

“What is the immediacy?” he asked. “That I’m going to eat one more bag of french fries before the court rules?”

Ms. Ng said there was urgency to the rule issued by the Board of Health to try to lower health risks associated with overweight New Yorkers.

“The problems are just getting worse,” she said, noting that 10 million meals each month would be eaten at the affected restaurants.

“Statistics indicate one bag of potato chips is not going to make a difference,” she said. “But even a modest reduction of calories over a short period of time — six months, a year — can make a difference.”

For the time being, the appeals panel left in place a stay of a lower-court ruling finding that it is constitutional for the city to force restaurants to post calories on their menu boards.

It appeared at one point in the hearing ready to lift that stay.

“What is the irreparable harm the restaurant association will suffer?” Judge Rosemary Pooler asked.

“You don’t want to represent that your food is fattening?” Judge Sonia Sotomayer quickly added.

A lawyer for the restaurant association, Kent Yalowitz, said restaurants believe federal laws pre-empted local efforts to try to regulate how restaurants describe the contents of their food. He said the First Amendment rights of restaurants protected them as well.

Judge Pooler noted that cigarette packages contain health warnings.

“If we were to adopt your view, no warnings would ever appear on anything,” she said.

Judge Sotomayer told Mr. Yalowitz that the appeals court would have to conclude that it was likely the restaurants will win to continue to block the city from implementing the rule.

Judge Pooler directed Mr. Yalowitz to send a letter to the FDA by tomorrow asking it to submit its opinion to the appeals court on whether the city was within its rights to force restaurants to post calorie counts.

The court indicated it would try to decide the merits of the issue by June 6, an expedited schedule that will require further arguments before the panel.