New Zealand has scored a major trade coup, becoming the first country in the world to start negotiating a free trade deal with Russia.

The decision to officially begin negotiations was announced last night by Prime Minister John Key and Russian president Dmitry Medvedev following a one-on-one meeting between the pair during this weekend's Apec summit in Japan.

Trade Negotiations Minister Tim Groser would not put a figure on the potential gains for New Zealand exporters, saying any predictions would be speculative.

However, Russia is seen as an increasingly well-off society with burgeoning demands for consumer goods. It already imports large quantities of food.

Groser said the deal was all about "future-proofing" New Zealand, which exports around $180 million worth of goods to Russia each year, mainly butter sheepmeat, fish and cheese.

Much of the deal has already been "pre-cooked", meaning substantial progress has already been made.

New Zealand was also the first country to secure a free trade agreement with China, which has seen two-way trade nearly double since it came into force.

Russia's motivation for the deal is to prove itself as a responsible trading partner and boost its case for membership of the World Trade Organisation. New Zealand gets special access to a rapidly growing and increasingly wealthy consumer maket.

Meanwhile, the Apec "silly shirt" tradition for leaders was to be extended to spouses this year.

Bronagh Key was measured for a kimono designed by Japanese fashion maestro Hiroko Koshino. John Key was not sure how his wife would look.

"If they have Bronagh versus Michelle Obama, she [Bronagh] will look like the Hobbit," he said, referring to the difference in height between the two first ladies.