NEW YORK - After months of resistance, several big fast food chains have finally begun obeying a first-of-its-kind New York City rule requiring some restaurants to post calorie counts right on the menu.

Burger King and McDonald's were among the chains that unveiled new menu boards Friday at scores of locations throughout the city.

They take calorie info that had long been available on Web sites and tray liners and put it front-and-centre above the cash register.

The calorie posting rule took effect in May, but legal action delayed enforcement until now.

Starting Saturday, chains big enough to fall under the rule will face penalties of up to $2,000 per store for not disclosing calorie info in a prominent spot on their menus, preferably next to the price.

To date, the lack of enforcement had meant haphazard compliance, and it remained unclear Friday how many of the estimated 2,500 covered restaurants would meet the deadline.

A few chains still appeared to be ignoring the rule, perhaps holding out hope that a court would block the plan, the first of its kind in any U.S. city.

An industry lawsuit is pending.

Other restaurants offered calorie info for some items, but not others, raising questions about whether they might still face fines.

The new rules are part of an anti-obesity campaign that has also included a recent city-wide ban on artificial trans fats in restaurant food.

A few restaurants appeared to be caught completely off guard by the calorie rules, especially the homegrown fast-food chains that pepper New York City's outer boroughs.

"This has been an absolute nightmare," said Enrique Almela, director of operations at Singas Famous Pizza, which has 17 restaurants, most in Queens.

The menu rule only applies to restaurants that serve standardized portion sizes and have 15 or more locations nationwide, a distinction that was intended to target fast-food giants.

But, in practice, the threshold is low enough to sweep up little-known outfits like Singas Famous, Golden Krust Caribbean Bakery and other local franchises that have never done nutritional testing before.

Almela spoke with The Associated Press from his car Wednesday as he rushed sample pizzas to a food laboratory on Long Island.

He said the tests to determine the calorie content of his 35 different pizza combinations will cost $10,000, and he doubts they'll produce accurate data.

"I may put 15 pepperoni on a pie. Someone else may put 12. We don't measure the amount of cheese we put on," he said. "If you put up roundabout numbers, how does that help anyone?"

They were not the only ones racing the clock.

Mister Softee vendors hurried to add decals containing calorie info to the sides of their trucks this week -- a temporary fix until the end of the ice cream season.

Company executive James Conway Jr. said he didn't realize his franchises were covered until last month.

The deadline also looked problematic for a unique class of New York City eateries: loosely affiliated, largely immigrant-owned restaurants that share the same name and sometimes the same suppliers, but operate independently.

City health officials said restaurants have had ample time to prepare.

The regulation was first passed in 2006 and received wide media attention. It was redrafted after a court battle struck down the original version.

Every restaurant licensed by the city got a letter this spring.

Another 250 were issued formal warnings when health inspectors noticed that they hadn't yet complied.