A chef slices high-grade fatty Atlantic bluefin tuna at a sushi restaurant in Tokyo. A UN body is hearing proposals to ban the export of the tuna prized by sushi lovers. (Itsuo Inouye/Associated Press)

Opposition grew Wednesday against a proposal to ban the export of Atlantic bluefin tuna, with several Arab countries joining Japan in arguing it would hurt poor fishing nations and was not supported by sound science.

Other countries, including Australia and Peru, have expressed support for a weakened proposal, which is expected to be introduced Thursday at the 175-nation Convention on International Trade in Endangered Species, or CITES.

They want the trade regulated for the first time by CITES but not banned outright as demanded by conservationists, who contend the Atlantic bluefin is on the brink of extinction.

"Most Mediterranean countries are afraid because they export this tuna," said Ahmed Said Shukaili, a delegate from the Persian Gulf country of Oman, whose nation will follow the Arab League position opposing the ban.

"They see this as an economic issue," he said. "There is a lot of concerns for the fishermen who depend on this fish."

Japan says it has the support of China while several other countries were undecided. China has not said publicly where it stands.

Monaco — the sponsor of the proposed ban on the export of Atlantic bluefin tuna — says numbers have fallen by nearly 75 per cent since 1957. But most of the decline has occurred over the last decade, with demand driven by sushi lovers in Japan and elsewhere for the bluefin's succulent red and pink meat.

Supporters of the ban, including the European Union and the United States, say it is necessary because the Atlantic bluefin is a migratory species that swims from the western Atlantic to the Mediterranean — putting it beyond any one country's border. Compounding the tuna's plight is the growing threat from illegal fishing fleets and the failure of existing measures to keep the population sustainable.

"The North African countries are concerned about fishermen losing their jobs," said Patrick Van Klaveren, a delegate with the Monaco delegation. "But nevertheless the jobs will be lost when there will be no more bluefin tuna. With bluefin tuna, it's not a question of 10 or 20 years but five or six years or less to see the stock collapse."

Raw tuna is a key ingredient in traditional dishes such as sushi and sashimi, and the bluefin variety — called hon-maguro in Japan — is particularly prized.

Japan, which imports 80 per cent of Atlantic bluefin and has led the opposition to the ban, argued on Wednesday that CITES should have no role in regulating tuna or other marine species. Japan said it is willing to accept lower quotas for bluefin tuna but wants those to come from the International Commission for the Conservation of Atlantic Tunas, which currently regulates the trade.

Masanori Miyahara, chief counsel of the Fisheries Agency of Japan, told The Associated Press that CITES was "unfair and partial" and that a tuna ban would allow the Europeans and Americans to continue fishing tuna domestically while Japan suffers from a steep drop in exports.

"The big players will continue fishing," Miyahara said. "If necessary, let's stop fishing using ICCAT measures. Then everyone must give up the fishing. But here, it is very unfair."

Critics, however, argue that ICCAT consistently ignores its own scientists in setting quotas and does little to stop countries from exceeding already high quotas or cracking down on widespread illegal fishing.