Canada will put forward a list of U.S. products that it will target in retaliation over a dispute with its largest trading partner about country of origin labels on meat, Agriculture Minister Gerry Ritz said on Friday.

The dispute stems from a 2009 U.S. requirement that retail outlets label the country of origin for meat and other products, in an effort to give U.S. consumers more information about their food.

Canada and Mexico complained that the rule caused a decline in U.S. imports of their cattle and pigs, and the World Trade Organization has ordered the United States to make changes by May 23.

"We will be putting forward a list of retaliatory products to make sure that the Americans have a further understanding of what that will be," Ritz said at an unrelated news conference in Saskatoon, Saskatchewan. "The process requires that it goes back to the WTO for a ruling on whether or not their changes are acceptable. Should they not be, then those retaliatory measures are assessed and put into play, and that process can take some months if not a year."

Ritz did not say which products are on the list, and his comments did not make clear whether Canada is sending the list of targeted products directly to the WTO for approval, or initially to the U.S. government in hopes of spurring last-minute changes.

The minister's spokesman, Jeffrey English, said in an email that Canada still hopes the U.S. will comply with the WTO by May 23, but is planning its next steps in case it does not. A spokeswoman for the U.S. Trade Representative could not be immediately reached.

(Reporting by Rod Nickel in Winnipeg, Manitoba; additional reporting by Doug Palmer in Washington; Editing by Gerald E. McCormick and Sofina Mirza-Reid)