Pyongyang has said it will launch a communications satellite between April 4-8, but regional powers believe the real purpose is to test a long-range missile, the Taepodong-2, which is already on its launch pad at a North Korean missile base.

"I have issued an order ... to prepare to destroy any object that might fall on Japan as a result of an accident involving a flying object from North Korea," Defense Minister Yasukazu Hamada told reporters after a meeting of Japan's Security Council.

North Korea has given international agencies notice that the rocket's planned trajectory should take it over Japan, dropping booster stages to its east and west. It has said any attempt to shoot down the rocket itself would be an act of war.

Hamada reiterated Japan's call for the reclusive state to cancel the launch and said Tokyo would do everything it could to protect the Japanese people. But he stressed that Japan would only act if the object threatened to fall on its territory.

In its only previous test flight in 2006, the Taepodong-2 either blew up or was deliberately destroyed after failing just after launch.

Japanese officials say the chances of debris falling on its territory are slim and have called on the public not to panic.

Top nuclear envoys from Japan, South Korea and the United States were to meet in Washington on Friday in a sign of growing concern over the launch, the first big test for U.S. President Barack Obama in dealing with the prickly North.

Russia said North Korea should abstain from testing the rocket and called for dialogue with Pyongyang, a day after Foreign Minister Sergei Lavrov cautioned the international community against making hasty decisions.

"We understand that the current situation in the region of North-East Asia is tense, and this is why it would be better if our partners in North Korea abstained from this, from this launch," Russian Deputy Foreign Minister Alexei Borodavkin said.