Prime Minister Shinzo Abe appears eager to join the talks on the Trans-Pacific Partnership free trade plan now being negotiated by 11 countries — the United States, Canada, Mexico, Peru, Chile, Australia, New Zealand, Singapore, Brunei, Malaysia and Vietnam. He is expected to announce his decision about the TPP talks this week.

Before that, he should carefully consider whether Japan’s interests will be served in the talks. At the very least, he should fully explain not only the merits and demerits of the TPP but also the difficulties associated with the procedure for joining the talks, which are veiled in secrecy.

It is clear that it would be virtually impossible for Japan, a latecomer to the talks, to change various rules already agreed on by participants now in negotiations, although the government has been mum on this point. This omission on the part of the government constitutes betrayal of people’s trust. How many participants will agree to a makeover of TPP negotiation procedures for the sake of Japan?

The TPP is different from ordinary free trade or economic partnership agreements. In principle, participating countries must agree to eliminate all tariffs. But the TPP is not only about the elimination of tariffs. It covers wide-ranging trade and investment rules for 21 fields including intellectual property, the environment, labor regulations, sanitary-quarantine matters and rules on orders for public works projects.

It is important to understand that agriculture, though important, is only one of the issues addressed by the TPP. Since participation in the TPP will greatly impact Japan’s economy and society, Mr. Abe cannot be too careful about his decision. The TPP could greatly affect the finance, insurance and medical sectors.

Mr. Abe should ask himself whether Japan, by taking part in the TPP talks, can protect a wide range of national interests. For example, how will participation affect the social policy fabric, including the public health insurance system that Japan has painstakingly established over many decades?

On the basis of his meeting with U.S. President Barack Obama at the White House and a Japan-U.S. joint statement issued on Feb. 22, Mr. Abe said it has become clear that the “abolition of all tariffs without exceptions” is no longer a prerequisite for joining the TPP talks.

This remark smacks of sophistry that misleads not only the public but also the Diet. The crux of the joint statement is that “the final outcome will be determined during the negotiations.” Even if Japan decides to join the TPP talks now, it is expected to take about three months before it can actually take part in the talks because of U.S. congressional procedure.

Since the current participants in the TPP talks are said to be aiming to conclude the talks by yearend, it must be asked, again, whether Japan will be able to achieve its intended goals during the limited negotiation time available.