May 19/UPI -- McDonald's Corp. says all its U.S. restaurants will be cooking with oil that is free of trans fats by the end of this year.

The year-end target is the most specific timetable that McDonald's has provided so far, but it is later than some industry experts and health advocates were expecting, Crain's Chicago Business reported Monday.

At its annual shareholder's meeting last May, the Oak Brook, Ill., company said only that the shift away from trans-fat oil would "be complete within a year."

The switch represents a huge challenge for McDonald's which uses more than 75 million pounds of oil each year to cook its french fries and chicken nuggets.

Customers flooded the company with complaints in 2002 when it announced plans to switch to a healthier oil.

"They have not progressed as quickly as many expected and (as) they indicated they might," Bob Goldin of Technomic Inc., a Chicago restaurant consultancy, told Crain's Chicago Business.

From the May 27, 2008, Prepared Foods e-Flash