Ibuki, concurrently chairman of the National Public Safety Commission, said there would be a 40-minute period of potential danger if the engines of the 140-ton, 108-foot (33-meter) Russian space station fail or misfire during a planned deorbit sequence set to send it plunging into the south Pacific as expected around Wednesday.

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''There is a very limited possibility that Mir will cause trouble to Japan, but I'll ask local governments to take measures just in case,'' he said.

The minister said he also told government officials in charge of crisis management to be alert around the clock from Tuesday through Thursday to deal with any incidents involving the 15-year-old Mir.

Russia says ''possibilities remain'' that Mir will pass over ''islands and seas southwest of Kyushu,'' suggesting it could fly in a southeasterly direction over the eastern coast of China, islands in Okinawa Prefecture, and Taiwan.

To deal with any contingency efficiently, Ibuki said he has instructed the National Police Agency and the Fire and Disaster Management Agency to work with prefectural governments and other pubic bodies to collect information and take emergency measures.

Russia has said Mir will plunge to Earth between March 21 and 23, a day later than previously scheduled.