WASHINGTON (Reuters) - The World Trade Organization's top court overstepped its authority this month in a ruling against a U.S. method of calculating anti-dumping duties, two senior U.S. lawmakers said Monday.

"The Appellate Body mistakenly asserts the authority to resolve disagreements that the WTO Members were unable to resolve through negotiation," House of Representatives Ways and Means Committee Chairman Charles Rangel and Trade Subcommittee Chairman Sander Levin said in a joint statement.

"Ultimately, this will make it more difficult to reach new agreements to liberalize trade. As we strive to complete the Doha Round of WTO negotiations, this report should give all negotiators cause for concern," the Democrats said.

The Ways and Means Committee plays a major role in consideration of U.S. trade agreements and has jurisdiction over U.S. anti-dumping and other trade remedy laws.

At issue is a U.S. method -- known as "zeroing" -- for calculating anti-dumping duties on imported goods, which has been repeatedly challenged at the WTO in recent years by the European Union and other trading partners.

International trade rules allow countries to impose duties on imports that are sold for less than they cost at home, if they are found to damage businesses in the importing country.