The impoverished South Pacific kingdom agreed on accession terms with the WTO in December 2005, but deferred formal ratification until last month to give itself time to improve its tariff system.

As part of its entry package, Tonga agreed to make several commitments to liberalize its trade regime, including lowering all import tariff lines to 15 or 20 percent within one year. The country also was required to eliminate all industrial subsidy schemes prohibited by the WTO by the final date of its accession.

The terms were criticized in 2005 by the international aid agency Oxfam, which noted that the United States and the European Union maintain much higher tariffs on imports such as beef and sugar.

The Oxfam report warned that because Tonga earns some two-thirds of its revenue from trade taxes, cutting tariffs would affect its ability to provide basic health care, education, water supply and other essential services.

Tonga, a 170-island archipelago about halfway between Australia and Tahiti, has an economy dependent on pumpkin and vanilla exports, fishing, foreign aid and remittances from Tongans abroad.

Bordering on bankruptcy, it faces mounting poverty and unemployment among its youth. The World Bank has said many of the nation's 114,000 people live on or below the poverty line.