Japan is planning to expand the scope of the foreign farm products it wants to continue imposing tariffs on under the Trans-Pacific Partnership free trade pact, sources said.

The Liberal Democratic Party-leg government has been seeking to protect the Japanese agriculture industry by making imports of five key farm product categories — rice, wheat, beef and pork, dairy products, and sugar — exceptions to the TPP's basic rule of tariff elimination.

But following a review of other product categories, they now deem pineapple should be included in the key categories along with beans. Plywood and fisheries products are also under consideration, the sources said Thursday.

Japan's pineapple production is concentrated in Okinawa and Kagoshima prefectures, and the government has deemed that eliminating the tariffs on imported pineapple products could devastate local businesses, they said.

Beans are necessary to maintain the country's crop rotation system, while plywood and fisheries products have similarly important roles.

As a member of the TPP talks for creating a high-level trade liberalization pact, Japan is aiming to bring the percentage of its tariff-free items to 95 percent or more. But keeping tariffs on the original five key farm product categories will only bring the percentage to 93.5.

Japan is currently reviewing the possibility of eliminating tariffs on some of the 586 items that fall under the five farm categories, but it is also trying to see whether there are other items outside of the five categories that need protection.

Under the 13 existing free trade agreements concluded by Japan, the percentage of items on which Tokyo agreed to eliminate tariffs within 10 years ranges from 84.4 percent to 88.4 percent of the total.

Having already held 19 rounds of talks over more than three years, the 12 countries in the TPP talks are aiming to conclude a deal by the end of this year.