A group of eight Pacific island countries agreed Friday to push ahead with plans to close off 4.
5 million square kilometres of high seas areas to fishing to save rapidly depleting tuna stocks.
Officials from the group known as the Parties to the Nauru Agreement (PNA) - which controls areas responsible for a quarter of the world's tuna supply - agreed to extend the ban to new areas on the high seas.
They plan to do this by requiring that fishing companies which want to fish in their economic zones have to agree to stop fishing in the targeted high seas areas.
They will take the proposal to the annual meeting in December of the Western and Central Pacific Fisheries Commission, a body which groups the Pacific island nations with fishing countries to agree on measures to conserve tuna stocks.
Two high seas pockets between the islands' economic zones have already been excluded from fishing from this year. The PNA wants to expand this from next year to include new areas from Palau and Papua New Guinea in the west to Kiribati in the east, and Marshall Islands in the north to Tuvalu in the south.
"It's not going to be easy (to get acceptance of the closure)," said Sylvester Pokajam, managing director of Papua New Guinea's National Fisheries Authority.
"But it will have a great impact on bigeye tuna that is being overfished."
Bigeye and yellowfin tuna are favourites for Japan's sushi and sashimi markets and scientists warn they are being overfished. The other common species in the area is skipjack, which is still believed to be plentiful and is used for canning.
Palau's marine resources director Nanette Malsol said she believed the closure would help in the fight against illegal fishing.
"There is a lot of illegal and unregulated fishing in high seas areas," she said. "Countries bordering these areas are struggling with it."
The PNA has set up a secretariat which was opened in Majuro this week to coordinate conservation measures and to increase the returns to island countries from the three-billion-US-dollar tuna fishery in the Pacific.
In addition to PNG and Palau, the PNA's members include the Marshall Islands, Nauru, Federated States of Micronesia, Kiribati, Tuvalu and the Solomon Islands.