While New Zealand's agricultural exporters are licking their chops at the prospects of Japan joining the Trans Pacific Partnership trade agreement, Professor Jane Kelsey of University of Auckland says Japan is a poison chalice for the talks.
Japan officially joined 11 other countries in the TPP trade negotiations this week.
New Zealand meat, dairy and horticulture sectors all welcomed Japan's addition - saying its market is already very significant and any lowering of its protectionist trade barriers would be a real boost for farmers and growers.
However, Professor Kelsey, a critic of the trade agreement, said Japan's presence will slow the negotiations enormously.
She said the chance of any deal being struck this year, as was hoped, is now gone.
Further, she said any genuine dairy concessions would cause a massive political fallout in Japan and that New Zealand can now kiss goodbye its quest for a gold standard trade deal.