Tension is escalating between China and Japan over exploration for oil and natural gas in disputed waters.
Japan's trade minister is calling China's latest reported action, granting rights for natural gas exploration in the East China Sea, an unfriendly act, and predicts it will trigger a diplomatic dispute.
Shoichi Nakagawa discussed the issue on a Sunday morning television show in Japan.
The trade minister says China has mapped out several areas for commercial exploration in what Japan regards as its exclusive economic zone.
Beijing and Tokyo have been feuding for months since Chinese government survey ships were spotted in the zone. Japan responded by starting its own mapping project in the waters, where official demarcation is not clear.
Japan also contends that the source of natural gas, in Chinese waters, is actually connected to Japanese territory under the sea.
The explorations are taking place near a group of disputed islands, called Senkaku in Japan, and Diaoyu in China. They are claimed by Japan, China and Taiwan.
Earlier this month, China's Foreign Ministry called for working level negotiations with Japan on the issue.
Japanese Foreign Minister Nobutaka Machimura on Sunday said his government wants to confirm exactly what China is doing in the disputed waters, and then say to Beijing "what it needs to say."
Meanwhile, Japanese diplomats will not confirm media reports saying Japan pressured international energy giant Royal Dutch-Shell into withdrawing from a gas project in the disputed waters.