Japan will urge North Korea at the upcoming summit in Pyongyang to stop sending vessels on espionage and other shady missions in the Sea of Japan, Chief Cabinet Secretary Yasuo Fukuda indicated Thursday, in light of the suspicious ship pursued the previous day.

"It is very possible" Prime Minister Junichiro Koizumi will take up the issue in his Sept. 17 summit with North Korean leader Kim Jong Il, Fukuda told reporters, adding, "The latest incident is unlikely to affect the schedule of the Koizumi-Kim meeting."

Suspicions are mounting in Tokyo that the unidentified vessel was a North Korean spy ship, due to its appearance and to indications it had a large stern hatch that could be opened to deploy a small submersible. "But we cannot conclude it was one," Fukuda said.