Japan's participation in a free-trade group led by the U.S., if it agrees, could open up the country's agriculture markets worth $48 billion to foreign exporters of rice, sugar and beef, boosting global prices.

Membership in the Trans-Pacific Partnership could lift sales for Tyson Foods Inc. and Fonterra Cooperative Group Ltd., as participants aim to eliminate import tariffs within a decade, according to Norinchukin Research Institute. Prime Minister Yoshihiko Noda, who risks splitting his party if he supports joining the trade talks, has said markets must be opened to boost the weak economy, which is struggling to recover from the March earthquake and nuclear disaster.

Tariff elimination could deepen the country's reliance on food imports to almost 90 percent from 60 percent, the agriculture ministry has forecast. Imports could tighten global supplies and boost prices of rice, which has gained 12 percent this year, and cattle futures, which have advanced 14 percent. Noda's Democratic Party of Japan is divided over whether to promote trade to lift economic growth or protect farmers who may be harmed by lower tariffs and increased competition.