US negotiators engaged in intense and fraught talks with Japan over forming a new Pacific trade partnership have been frustrated by Tokyo’s resistance to cutting agricultural tariffs, as well as domestic resistance to the mooted agreement within the US Congress, writes James Politi in Washington.

Even as the Trans-Pacific Partnership talks have entered their final stages over the past few months, the US administration has failed to secure important legislation which would make it easier to pass trade deals swiftly and with no amendments through Capitol Hill.

Without such a guarantee, known as Trade Promotion Authority, it is harder for the US to extract the make-or-break concessions from other countries, including Japan – customary at the eleventh hour – owing to fears that the agreement may have to be renegotiated once it is up for congressional approval.