There are concerns that international cooperation to prevent North Korea from developing nuclear weapons and missiles could be in jeopardy if Tokyo lifts trade sanctions against the North.

Tokyo and Pyongyang agreed last Thursday that Japan will lift sanctions imposed on the North if Pyongyang investigates a bizarre abduction campaign of Japanese people during the 1970s and 80s.

Currently, trade between Japan and the North is at zero after Tokyo banned imports from the isolated country in 2006 and exports to it in 2009 over its nuclear and missile programs.

In 2000, Japan was the North's second largest trading partner with a trade volume of US$438 million accounting for 19 percent of the North's entire annual trade volume, a close second after China's $484 million.

In 2001 Japan gave the North rice and other humanitarian aid, bringing the figure to $1.2 billion ahead of China's $721 million.

A researcher at a think tank said given that North Korea's trade volume was $7.3 billion last year, trade between Tokyo and Pyongyang could jump to $1 billion if Japan partially lifts sanctions and to $2 billion if it lifts them completely.

This would seriously undermine the sanctions imposed by other countries.

International sanctions based on UN resolutions are restricted to luxury goods and technologies and funds related to nuclear and missile development. Japan imposed its own complete trade ban on top of that.

The first sanctions to go under the agreement with North Korea would be bans on human exchanges, money transfer and the entry of ships. The other trade sanctions would be lifted step by step as the North Korean investigation proceeds.