France will support a ban on global trade in bluefin tuna, a government official said today, bowing to environmentalists' concerns about stocks of the giant fish found mainly in the Mediterranean.

France's iTele news channel reported that the proposed ban would not come into force for 18 months. There was no immediate confirmation of this and full details of the French stance were due to be released later in the day.

Environmentalists have warned that a prolonged delay to any ban would prove disastrous to bluefin tuna stocks and could lead to the extinction of the species.

Monaco has proposed protecting bluefin tuna, much prized by sushi fans in Japan and around the world, by listing it under appendix I of the Convention on International Trade in Endangered Species (CITES).

"France's position is to support Monaco's proposal to list bluefin tuna under appendix I of CITES," a government official, who requested anonymity, told Reuters.

The decision could anger fishermen in France and other fishing nations as bluefin tuna commands high prices in Japan, where 80 percent of the catch is exported.

The European Union has come close to supporting the proposal, but fishing nations Spain, Italy, France, Cyprus, Greece and Malta last September voiced their opposition.

France's policy change could be decisive at the next CITES meeting in Qatar in March, after Italy said last week it would back a ban.