North Korea said on Saturday it has finished preparations for a satellite launch which would go ahead "soon", keeping the world guessing about the timing of what critics see as a disguised missile test.

In a sign of frayed nerves, Japan's government at one point said the rocket launch was thought to have gone ahead, only later to retract its statement as incorrect.

The nuclear-armed communist North says it plans a peaceful satellite launch sometime between 4 and 8 April and has defied demands from the United States and Washington's regional allies to call it off.

Preparations to launch an "experimental communications satellite" have been completed and it will be launched soon, the state Korean Central News Agency announced.

It said the satellite would be carried by an Unha-2 (Galaxy-2) rocket — known in the West as the Taepodong-2 which could theoretically reach Alaska or Hawaii at maximum range.

Breach of nuclear deal

Washington, Seoul and Tokyo have vowed to take a launch to the UN Security Council as a breach of a resolution passed after the North's 2006 missile and nuclear tests.

Pyongyang has said even a debate in the Council on the subject would lead to a breakdown of long-running six-nation nuclear disarmament talks.

It has notified world aviation and shipping agencies that blast-off will be between 11am and 4pm (0200-0700 GMT).

Weather conditions were not ideal on Saturday at the Musudan-ri launch site on the northeast coast, Seoul experts said, with fairly strong winds and cloud.

The weather agency said the wind was expected to die down Sunday morning, but the area would stay cloudy.

YTN television, quoting Seoul military sources, said the North has not yet switched on radar systems at Musudan-ri.

It said such radar signals had been detected several hours before previous launches. Seoul security officials declined comment.

South Korea, the United States and Japan have all deployed missile-tracking Aegis warships in the Sea of Japan (East Sea) to monitor the flight path.

The North has said the rocket's first stage will fall in the sea 75 miles west of Japan and the second stage will plunge into the Pacific.

Pressure from Obama

US President Barack Obama urged Kim Jong-Il's regime to desist.

"We have made very clear to the North Koreans that their missile launch is provocative," he said Friday in Strasbourg.

"Should North Korea decide to take this action, we will work with all interested parties in the international community to take appropriate steps to let North Korea know that it can't threaten the safety and security of other countries with impunity."

Obama's special envoy for North Korea Stephen Bosworth gave an apparently softer message, saying that his goal is to resume stalled six-nation nuclear disarmament talks no matter what happens.

Analysts say a successful launch would give the regime a major propaganda boost amid lingering uncertainty over Kim's health, following reports that he suffered a stroke last August.

The launch aims to persuade the new US administration to open direct talks with Pyongyang, and will strengthen the regime's hand in future negotiations over its nuclear programme, analysts say.

The North tested a Taepodong-2 for the first time in July 2006 but it failed after 40 seconds.

In Seoul, South Korean President Lee Myung-Bak called an emergency meeting of security-related ministers.

South Koreans cancelled trips to Pyongyang on government advice, and almost all already in the North's capital left the country, the unification ministry said.

China, the North's sole major ally, is thought likely to block any bid for new UN sanctions.

The Security Council could toughen observance of existing sanctions — which ban trade in missile components, other weapons and luxury goods — or issue a chairman's statement criticising Pyongyang.

If North Korea goes ahead, Bosworth told a Washington news conference, the United States would "consult vigorously" on what action to take.

But he added that the aim is to get back to the denuclearisation process as soon as possible after the "dust settles."