GENEVA — On Nov. 19, the World Trade Organization (W.T.O.) began investigations into a European Union ban on American poultry, according to The Canadian Press.

For more than a decade, Washington and Brussels have argued over E.U. restrictions on U.S. poultry imports treated with four anti-bacterial chemicals: chlorine dioxide, acidified sodium chloride, trisodium phosphate and peroxyacids. Although each chemical has been approved for poultry processing by the U.S. Food and Drug Administration and the U.S. Agriculture Department, the European bloc placed a ban on poultry carcasses processed with such treatments in 1997.

During the final days of George W. Bush's presidency, the U.S. took the dispute to the W.T.O. The Obama administration is now moving forward on the case.

The W.T.O. panel reviewing the poultry complaint is expected to deliver a ruling within nine months.