Reports from Washingtonclaimed that rocket fuel was delivered last week to a missile test site on the east coast of North Korea. American intelligence monitoring was also said to have detected increased radar activity at the site, suggesting that the North Koreans might be preparing to track a missile after it was launched.
The reports are the latest in a spate of alarming rumours to have emerged from Washington, Tokyo and Seoul in the past fortnight. They have led to speculation that East Asia may be on the verge of a new and potentially dangerous crisis involving one of its most unpredictable and intransigent governments.
There was outrage in Japan at the end of last August when a North Korean rocket was unexpectedly fired over the northern part of the country. The government in Pyongyang insisted that it was the rocket for a broadcast satellite, launched to beam down patriotic songs. American intelligence concluded that it was a Taepo Dong I, a long-range missile capable of striking targets in a range of 1,240 miles, encompassing all of South Korea and Japan.
The missile allegedly being primed now is said to be the more powerful Taepo Dong II, capable of flying 3,700 miles, as far as Hawaii and Alaska.
Independent confirmation of the reports is impossible in North Korea, which allows only a handful of foreign diplomats and aid workers to live under tight restrictions in the capital, Pyongyang. Several times in the past year, South Korean and Japanese newspapers have quoted anonymous intelligence sources inaccurately predicting an imminent launch.
But whatever the North's real intentions, it is doing nothing to discourage speculation about a test. "We warn the United States once again that whether we launch a satellite or missile, it is our sovereign right," a North Korean diplomatic spokesman said last week.
"If the United States projects a `military countermeasure', we [North Korea] will retaliate against it with a stronger countermeasure."
A ballistic missile test would cause intense alarm at a delicate moment in Pyongyang's relations with the outside world.
Ever since Korea was divided into the communist North and capitalist South at the end of the Second World War, the countries have been among the tensest and most militarised on Earth. After the 1950-53 Korean War, the two sides never got round to signing a peace treaty.
Last week in Geneva they met diplomats from China and the US in the latest round of talks aimed at reducing tensions. The question of the expected missile test was not raised - since their discussions began in December 1997, the four parties have not even been able to agree on an agenda for their discussions.
The Japanese government said last week that it does not expect a test during August or September. But American missile tracking ships are reported to have been deployed to Japan, and last week, for the first time, Japan held joint naval exercises with South Korea in the sea between the two countries.