The US government is also a major revenue source for Tuvalu. In 1999, the payment from the South Pacific Tuna Treaty (SPTT) was about $9 million, with the value increasing in the following years. 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) for 18 months.