Vietnam said the United States has improperly used the zeroing methodology, which usually translates in an increase of anti-dumping duties on foreign producers, and other practices inconsistent with the WTO.

Vietnam also claimed that the United States has broken rules on dispute settlement, with Vietnamese exporters’ requests for revocation of anti-dumping measures being routinely denied despite the fact many of the exporters are eligible for such a revocation. One such company that has been denied a revocation request is Vinh Hoan Corp., a major exporter of pangasius to the United States.

The United States has 60 days to settle the complaint; otherwise Vietnam could request adjudication from the WTO.

“The United States imposed higher anti-dumping duty on Vietnam pangasius products last year and Vietnam had no other way but complained to WTO to challenge it,” Nguyen Tien Thong, a seafood expert from the University of Southern Denmark, told SeafoodSource.

The value of Vietnam’s pangasius shipments to the United States fell 9.7 percent year on year to nearly USD 320 million (EUR 261 million) during January-November 2017. Vietnam’s Association of Seafood Producers and Exporters (VASEP) earlier this month attributed the drop to U.S. higher anti-dumping tariffs and stringent inspections against Vietnamese products.

The United States is the top destination for pangasius from Vietnam, but the country is shifting its exports to China as the U.S. institutes more protectionist trade measures.

About 90 percent of pangasius imported by the United States is from Vietnam, but its more widespread acceptance in the U.S. market was beginning to threaten U.S. catfish growers and wholesalers, who pushed for political changes to discourage imports of foreign catfish species such as pangasius, according to Thong.

Vietnam had already filed two complaints to WTO over U.S. anti-dumping measures on certain shrimp from Vietnam. The shrimp dispute between the two countries began in 2010 but only ended in 2016 when the United States agreed to remove duties on Vietnamese shrimp exporter Minh Phu Seafood Corp. and to refund duty deposits the Vietnamese firm had paid.