Japan's Foreign Minister Taro Aso and US envoy Thomas Schieffer met in Tokyo amid increasing speculation that Pyongyang is set to conduct a launch.

Officials believe that Pyongyang may be planning to test the Taepodong-2, a missile with a range of up to 6,000km.

Mr Schieffer urged North Korea not to take "provocative action".

Such a move would lead to further isolation from the international community, he said.

Mr Aso described the situation as serious and said that Japan had warned North Korea against going ahead with a test.

The message was sent via diplomatic channels in Beijing, according to Japanese media reports.

Site activity

The meeting followed reports in the regional media that North Korea was stepping up its work towards a test.

South Korean daily Chosun Ilbo reported that booster rockets had been loaded onto a launch pad and 10 fuel tanks moved to the site in the north-east of the country in preparation for a launch.

The information came from US and South Korean satellite images of activity at the site, the daily said, citing an unnamed government official.

A Japanese daily, the Sankei Shimbun, reported that the missile could be fired as early as Sunday, citing unnamed government officials.

Japan is acutely worried by this, says the BBC's Chris Hogg in Tokyo. The government says any launch would threaten the country's security.

North Korea last tested a long-range missile in 1998, when it fired the Taepodong-1 missile, with a range of 2,000 km, over northern Japan. The missile landed in the Pacific Ocean.

Diplomats say that North Korean technicians are going through the same procedures that were undertaken before the test in 1998.

A successful test of the Taepodong-2 would put parts of the US within striking distance of Pyongyang.

(BBC)