One possible result: Most beef in supermarkets will carry the American label, said John Lawrence, an agricultural economist at Iowa State University. Meatpackers may opt to send beef from cattle born in Mexico to restaurants, which are exempt from the labeling law, and reserve U.S. beef for supermarkets, he said.

Lawrence said it's too soon to tell whether the labeling requirements will increase food prices or boost the prices received by producers.

Congress passed a labeling law in 2002, but its implementation was delayed for all but seafood because of objections by meatpackers, retailers and some producers. The industry agreement, negotiated under pressure from lawmakers, will be part of a farm bill that the full House will vote on as early as next week.

Seafood has been labeled with the country of origin for two years now without any significant impact on sales, according to industry officials.

Country-of-origin labeling "does not really register" with shoppers, said Stacey Viera, a spokeswoman for the National Fisheries Institute. "They might say it does, but intent and practice are two different things."

Still to be worked out by lawmakers is labeling for fresh fruits and vegetables, which also were covered by the 2002 law. The House committee wants the produce industry to reach an agreement before the House votes on the farm bill.

Key to the deal was a method for labeling pork from pigs born in Canada that are fattened on corn in Iowa and other states, and for beef from Mexican- or Canadian-born calves.

Under the agreement, those products would be labeled as a product of the United States and Canada or a product of the United States and Mexico.

Similarly, packages of ground beef would have to list all the countries of the cattle that went into the product. Such a label might say: "Contains beef from Australia, Mexico, Argentina and the United States."