U.S. health regulators plan to give restaurant companies more time to comply with new rules that require clear calorie and nutritional information on menus.

Under the healthcare law passed in March, restaurants must clearly post calories and other nutrition details on their menus. The rules target restaurants with 20 or more locations, as well as other retail food outlets, and would affect huge national chains like McDonald's Corp and Yum Brands Inc, the operator of the KFC, Taco Bell and Pizza Hut fast-food chains.

The U.S. Food and Drug Administration has until March 2011 to put these rules into effect. But the agency said on Tuesday it would hold off on enforcing them for an unspecified time period so that companies could make the changes. It also asked for public comment on how long to refrain from enforcement.

Other companies likely to be affected by the new menu rules include Starbucks Corp, Olive Garden and Red Lobster owner Darden Restaurants Inc, and IHOP and Applebee's parent DineEquity Inc in March began adding calorie counts to its menu boards ahead of the national requirements.

Nevertheless, most major chains have resisted posting such information without legislation and the threat of fines. Several states, counties and cities have proposed or passed laws requiring menu labeling, but only a handful -- including New York City -- have put them into effect.

The FDA posted the draft guidelines on its website here