In a briefing to the World Trade Organization (WTO), Japan said it is monitoring radioactive contamination to prevent potential food safety risks and will provide the WTO with quick and precise information.

"In return, Japan asked members not to overreact," said a WTO official.

Several countries have banned milk and produce from the areas near the damaged Fukushima Daiichi nuclear plant, 240 km (150 miles) north of Tokyo, due to contamination fears. Japan has itself stopped exports of vegetables and milk from near the plant, which is leaking radiation.

As radiation fears linger, Singapore has told the UN nuclear watchdog that some cabbages imported from Japan had radiation levels up to nine times the levels recommended for international trade.

While food makes up only 1 percent of Japan's exports, the tsunami-crippled nuclear plant poses a serious risk to an economy burdened with huge public debt, an aging population and a big bill for rebuilding, possibly topping US$300 billion.

Radioactive iodine in the sea off the damaged plant has hit record levels. The state nuclear safety agency said the amounts were 3,355 times the legal limit and highly toxic plutonium has been detected in the soil at the Fukushima Daiichi plant.