Japan is ready to shoot down any North Korean rocket headed toward its territory, Japan's defence minister warned Tuesday, weeks after Pyongyang announced it would launch a satellite.

North Korea has said it is ready to launch what it calls an experimental communications satellite despite growing appeals from countries that suspect Pyongyang is planning a missile test to call off its plans.

The United States and its Asian allies see such a launch as a pretext to test the Taepodong-2 missile, which could theoretically reach Alaska.

"If there's a possibility that an object could lose control and drop on Japan, the object becomes our target, including a satellite," said Defence Minister Yasukazu Hamada.

"It's only natural for us to deal with it."

The Kyodo news agency, quoting an unnamed defence source, reported that Japan is considering deploying two Aegis-equipped destroyers carrying the Standard Missile-3 interceptor to the Sea of Japan (East Sea).

"We would have no other choice but to intercept," a senior Maritime Self-Defence Force officer was quoted as saying, referring to a scenario in which a missile or a rocket was launched and believed headed for Japan.

Defence ministry spokesman Katashi Toyota declined to confirm the report.

"I am aware of the reports. However I wouldn't comment on the movement of the Self-Defence Forces in specific cases, particularly what action the forces will take or are taking, due to the nature of this issue," he said.

Japan's Prime Minister Taro Aso signalled on Monday that a North Korean rocket launch -- even one carrying a satellite -- would lead to UN Security Council sanctions against the communist state.

The communist state has previously tested a missile under the guise of a satellite launch, and analysts say recent comments from the North indicated it was on the verge of another attention-grabbing test.

Japan and the United States have been working on a more advanced missile shield after North Korea in 1998 fired a missile over Japan's main island.

The defence ministry has installed US-developed Patriot Advanced Capability-3 surface-to-air interceptors in Tokyo and other parts of Japan.

As well as equipping two warships with Standard Missile 3 interceptors, in December it successfully shot down a ballistic missile in space high above the Pacific Ocean as part of a joint programme with the United States.