Prime Minister Shinzo Abe is facing a major challenge ahead of his summit with U.S. President Barack Obama later this month, as calls have mounted within the ruling Liberal Democratic Party for Japan not to participate in U.S.-led free-trade talks.

Abe, who heads the LDP, and his aides at the prime minister's office apparently want the country to join in the Trans-Pacific Partnership talks, which hold both the promise of opening up more foreign markets for Japanese exporters and the threat of dealing a serious — if not critical — blow to the agricultural sector, in particular rice and cattle.

But apparently most Diet members from the LDP, which has long depended on the rural vote, oppose Japan joining the ongoing TPP talks. The farm sector, including the long-subsidized rice growers, is both a major source of votes and funds for the party, and an Upper House election looms large this July.