Tokyo has upped the ante in a looming face-off over North Korea's planned rocket launch next month by vowing to shoot it down if it threatens Japanese territory.

Japan's cabinet issued the destroy order to the Minister of Defence, Naoki Tanaka, yesterday, giving him the green light to intercept the rocket "if necessary". Surface-to-air missiles have already been deployed in central Tokyo and southern Japan, near the missile's expected flight path.

The threat follows the release of private satellite photos apparently showing preparations for the launch at Tongchang-ri. The launch has been timed to coincide with the 100th anniversary of the birth of the North's founding father, Kim Il-sung, on 15 April, though it could come a few days before or after that.

Washington and its allies, including Japan, say the rocket launch is a test for long-range ballistic technology but Pyongyang insists it will put an observation satellite into space. The North's Central News Agency called the launch a "legitimate exercise" of its "inalienable sovereign right to peaceful exploration of outer space, universally shared by every member of the world".

Pyongyang's Committee of Space Technology says it has invited a team of foreign space experts and journalists to observe the satellite take-off to show "transparency". "Obviously, there is nothing to conceal," it said.

The US cancelled much-needed food aid to the North this week after the country's leadership rejected a direct appeal from President Barack Obama to abandon the launch. Mr Obama said the rocket would "further isolate" Pyongyang and lead to more sanctions. Critics of the launch say it violates UN Security Council resolutions that ban Pyongyang from engaging in ballistic-missile technology.

South Korea has also vowed to intercept the rocket if it strays over its territory. The increasingly uncompromising diplomatic tone as the launch nears raises the possibility of conflict escalating if Pyongyang reacts belligerently in a region with growing tensions. This week China accused the US and its allies of using the rocket launch as a pretext to install a missile defence system.