Companies that account for more than 90 percent of the nearly 10 billion chickens produced in 2005 in the U.S. have signed up for the testing program and said it expects more to follow, according to the National Chicken Council, a trade group that represents producers.

''We just want to assure people of the safety of the food supply,'' council spokesman Richard Lobb said.

Consumption of chicken in the U.S. has held steady despite worries about a bird flu strain that has infected millions of birds throughout Asia and parts of Europe and has killed 74 people.

The average person in the U.S. ate 85 pounds of chicken last year, compared with 84 pounds in 2004, according to the Agriculture Department.

Chicken prices at the grocery store have dropped in recent months, mostly because production is up and exports are down, said David Harvey, a poultry analyst for the department's Economic Research Service.

The council did not say what companies are participating, although Lobb said, ''Practically all the big ones are in it.'' Tyson Foods Inc. has more than one-quarter of the market, followed by Pilgrim's Pride Corp., Gold Kist Inc. and Perdue Farms Inc.

Tyson has been testing for bird flu and expanded efforts last fall, a spokesman said. The company now tests all of its flocks and conducts 15,000 tests each week, he said. Pilgrim's Pride said Thursday it was joining in the testing program.

Lobb said many companies already are testing ahead of the program's start on Jan. 16. The program is voluntary. Companies will cover the costs; the council said it does not have cost estimates.

The plan is for 11 birds to be tested from each chicken flock, or farm. By the council's estimates, that would mean more than 1.6 million chickens would be tested.