PARIS  Japan will not join in any agreement to ban international trade in Atlantic bluefin tuna under the United Nations treaty on endangered species, the country’s top fisheries negotiator said.

The negotiator, Masanori Miyahara, said in a telephone interview this week that Japan “would have no choice but to take a reservation”  in effect, to ignore the ban and leave its market open to continued imports  if the bluefin tuna were granted most-endangered species status.

“It’s a pity,” he said, “but it’s a matter of principle.”

Mr. Miyahara, Japan’s top delegate to the United Nations Convention on International Trade in Endangered Species of Wild Fauna and Flora, referred to as Cites, said the convention was the wrong forum for managing the fishing of the bluefin tuna.

Image A French retailer checked bluefin tuna. Japan objected to conservation and management of the fish by the United Nations. Credit... Christophe Ena/Associated Press

A formal proposal for a ban  which requires the approval of two-thirds of its 175 member countries  is scheduled to be presented at a Cites meeting next month in Doha, Qatar.