Japan could also survey around the disputed isles located in the overlapped Exclusive Economic Zones (EEZ) respectively claimed by Japan and South Korea to counter its neighbor's possible research action in the water, Japanese Vice Foreign Minister Shotaro Yachi warned on Monday.

Yachi's warning followed leaving of port of South Korea's research vessel for the contentious task. He implied on a press conference that a Coast Guard maritime survey similar to the one planned and aborted in April would be Japan's countermeasure, Kyodo News reported.

The South Korean research ship "Ocean 2000" started in early morning its mission, which intends to survey ocean currents around the two disputed islets known as Takeshima in Japan and Dokdo in South Korea, in the Sea of Japan (the East Sea). The islets are currently controlled by South Korea but are also claimed by Japan.

Japanese Prime Minister Junichiro Koizumi on Monday night asked South Korea not to be "too emotional," government sources were quoted as saying.

Earlier in the day, Japanese Foreign Minister Taro Aso and Chief Cabinet Secretary Shinzo Abe respectively urged South Korea to exercise self-restraint on the contentious issue.

During a phone talk with South Korean Foreign Affairs and Trade Minister Ban Ki Moon, Aso said it would be "extremely regrettable" if the South Korean government proceeds with the survey, but failed to make a breakthrough by the conversation, Kyodo said.

Abe for his part called on South Korea to make a "sensible decision," and warned that Japan will take "appropriate" action based on the UN Convention on the Law of the Sea and other relevant domestic laws if South Korea begins the research.

The South Korean side indicated that the survey will go on through July 14, said the report.

In April, Japanese Coast Guard vessels' intended marine survey around the disputed islets nearly led to a military confrontation with South Korea. The Japanese government said the planned survey came in response to South Korea's move to propose naming the sea-floor topography of the area on an international conference.

The two countries later reached a compromise through a vice ministerial meeting in Seoul, but their EEZ negotiations held in Tokyo in mid June failed to produce any tangible results except for an agreement to hold further talks in September.

(Xinhua News Agency July 4, 2006)