The panel was established on Friday, an official from the World Trade Organization (WTO) said.
The decision was taken after Vietnam made its second request at a closed-door meeting of the WTO’s Dispute Settlement Body, in line with WTO rules. No further details were immediately available on the row.
Vietnam says Washington has broken WTO rules in the way it has imposed punitive tariffs on Vietnamese fish it claims are being dumped, or sold at an unfairly cheap price, on the U.S. market.
U.S. imports of fish fillets from Vietnam have grown from $100 million in 2007 to more than $520 million in 2016. That made Vietnam the third-biggest U.S. supplier after Chile and China and the U.S. the top export market for Vietnamese fish.