Query: Of what did Tuvalu agree to the extension ?
Context: Tuvalu is also a member of the Nauru Agreement which addresses the management of tuna purse seine fishing in the tropical western Pacific. In May 2013 representatives from the United States and the Pacific Islands countries agreed to sign interim arrangement documents to extend the Multilateral Fisheries Treaty (which encompasses the South Pacific Tuna Treaty) to confirm access to the fisheries in the Western and Central Pacific for US tuna boats for 18 months. Tuvalu and the other members of the Pacific Island Forum Fisheries Agency (FFA) and the United States have settled a tuna fishing deal for 2015; a longer term deal will be negotiated.