Japan's diplomatic corps has sounded the right note of caution in response to the decision by North Korea to return to six-party disarmament talks. Although the breakthrough is encouraging — and President Bush rightly credited China with using its leverage with its trading partner — it's not yet time for celebration.

This week's developments inject a welcome ray of light into the darkened diplomatic arena. North Korea has boycotted talks for a year after the U.S., concerned that the rogue regime might be scheming to sell weapons of mass destruction, imposed stiff sanctions.

A pair of nuclear tests on North Korean soil convinced China that its own interests were at stake. Chinese officials helped broker the deal, reportedly cutting off oil supplies to its neighbor and dispatching an envoy to lodge a protest with North Korea's leader, Kim Jong Il. Progress also was aided by the U.S. agreement to put its year-old sanctions back on the negotiating table.

However, Taro Aso, Japan's foreign minister, underscored that his country would not accept a resumption of talks if North Korea insists on retaining its nuclear weapons — and he's right.

The emphasis must remain on prodding Pyongyang toward relinquishing all nuclear weapons, and sanctions — especially including those imposed by the United Nations — should be lifted only incrementally once there's verifiable evidence of progress.

Providing economic incentives, including allowing South Korea to provide electrical power to the North, as well as humanitarian aid, is key.

North Korea must be persuaded that its best interests are served by giving up membership in the nuclear club.