Japan will use weekend talks with North Korea to ask about reports the North has been preparing a missile test.
N Korea has already proved it has missiles, by publicly testing them
US and South Korean intelligence has picked up signs a test may be planned, though Japan's Prime Minister Junichiro Koizumi said the chances seemed low.
"It is necessary to find out what is going on," said Japan's chief cabinet secretary, Hiroyuki Hosoda.
The talks in Beijing will focus on the issue of missing Japanese which North Korea is believed to have kidnapped.
Rumours of a possible North Korean missile test have been circulating for several days, though South Korean and Japanese officials have played down the threat, saying troop build-ups around missile sites were probably just military exercises.
Map shows range of Taepodong 1 missile, flown over Japan in 1998. Range 1,500-2,000 km, payload: 1,000 kg
Evidence that North Korea working on testing Taepodong 2. Range up to 8,000 km (could reach western US)
Evidence from Jane's Defence of a pair of new ballistic missiles - one sea-based
Other missiles: Scud-B: Range 300 km, payload 1,000 kg
Scud-C: Range 500 km, payload 7600-800 kg
Scud-D (Nodong): Range 1,000-1,300 km, payload: 700-1,000 kg
On Thursday, US Secretary of State Colin Powell warned North Korea against breaking its moratorium on missile tests.
""I think it would be very unfortunate if the North Koreans were
to do something like this," he said.
Analysts are divided over the likelihood of a missile test at this stage.
North Korea has launched missiles before when it wanted to grab the world's attention in its demands for economic and diplomatic concessions.
But it is locked in a stand-off with the US over its nuclear ambitions, and appears to have ruled out further progress until after the US presidential election.
Six-nation talks on the nuclear issue, which were due to have resumed before the end of September, have now been put on hold.
North Korea has indicated it is prepared to continue its bilateral talks with Japan over the issue of the Japanese missing.