Japan and Thailand remained at loggerheads Tuesday over whether to enter formal negotiations to conclude a bilateral free-trade agreement as differences over Japan's politically sensitive farm sector continued to get in the way.

During a two-day meeting, officials from working groups on both sides continued to exchange views on possible areas of future FTA talks such as trade and investment, and financial services and agricultural cooperation, participants said.

While making headway in some areas, the question of how to address Japan's tightly protected rice market remained unresolved, and it is unclear when the two nations will be able to commence formal talks.

"As far as the rice issue is concerned, we haven't found common ground yet. We cannot start formal negotiations unless the Thai side gives up rice," a Japanese official said.

Despite the deadlock, Thai delegation chief Pisan Manawapat, director general of the Foreign Ministry's International Economic Affairs Department, was optimistic about an early start to formal talks.

"I hope it will start within this year," he said.

Japan and Thailand held working group meetings in Bangkok in September and in Tokyo in November. Beginning with the third session, the group was joined by representatives from the nations' business sectors, including people from the Japan Business Federation (Nippon Keidanren) and the Federation of Thai Industries.

The countries will hold the next meeting in Tokyo sometime in the coming months.