European officials are increasing pressure for an international ban on the commercial fishing of bluefin tuna. But they are facing a delicate balancing act as they try to weigh economic interests of a Mediterranean fishing industry, a sushi-loving Japan, and a species that some experts say is on the verge of extinction.

In the latest move toward protecting the fish, France said Wednesday that it would back a ban starting late next year on international trade in bluefin, which are found in the Atlantic as well as the Mediterranean Sea. About 80 percent of the bluefin catch is exported to Japan.

France’s backing for a ban comes with strings attached. Mr. Borloo and Bruno Le Maire, the French agriculture and fisheries minister, said support was conditional upon an 18-month delay in implementation, which they said was to obtain additional scientific data. The delay would allow two more fishing seasons to pass.

They also said a ban should not affect sales of bluefin tuna caught by line and pole or by longline within Europe. Like Italy, France will also seek financial aid from the European Union to help the fishing industry.