The government reached an agreement with Tokyo-based developer Taston Airport in January to buy the 8.2 sq km island for 4.5 billion yen. That deal collapsed in May when a new president of the company took over and demanded more money. The government agreed to increase its offer after taking into account the money Taston had invested.

The Japanese government has been seeking a suitable location for a training facility since it agreed eight years ago to provide US forces based in Japan a new site for landing practices.

US aircraft are not currently allowed to carry out flight practices at bases on mainland Japan due to noise pollution constraints. Instead, aircraft from the US airbase at Iwakuni in central Japan must fly about 1,400km south to Iwo To, better known as Iwo Jima. Mageshima is only 400km from Iwakuni, making it an ideal site.

Iwakuni Mayor Yoshihiko Fukuda hailed the central government’s announcement as a “big step forward”.

“Building a permanent training facility is necessary to reduce worries among local people [in Iwakuni],”he said. “We’d like to ask the government to have the facility completed early.”

As soon as the transaction is finalised, the Japanese government plans to build infrastructure for the Self-Defence Forces on the island, to be shared with US forces. Tokyo also plans to transfer some of the US troops stationed in Okinawa to the island to reduce the burden on local residents aggrieved by US military presence. Tokyo could consider relocating training for Osprey transport aircraft which have been involved in several incidents in Okinawa in recent years.

Tokyo plans to assume control of the island for its military with one eye on potential security challenges, said Garren Mulloy, a professor of international relations at Japan’s Daito Bunka University.

Work resumes on US base in Okinawa despite local objections and resentment

“This now gives Japan an increased range of options,” he said. “If the need should ever arrive for Japan to increase its capacity in the southwest, it now has the ability to do that.

“The Air Self-Defence Force urgently needs bases and runways because a lot of its facilities are already close to maximum capacity and have limited space to expand.”

Mulloy also said a new base would allow the Japanese military to no longer share facilities with civilian airlines, as it does at Okinawa’s Naha Airport.

Explained: Diaoyu/Senkaku islands dispute

“Japan may not need to have additional capacity now but many things could change in the next five, 10 or 20 years,” Mulloy said, with regard to the dispute over the sovereignty of the Diaoyu Islands.

“Japan is likely to move more and more units to its southwest as this will give it the capacity to smoothly transition to this new operational sphere.

“I do not anticipate any reaction from China as it is not as if they are doing this on one of the Senkaku islands, which would have been seen as provocative. But this does give the SDF an improved operational configuration.”

Mageshima is also sufficiently remote for Japanese or US forces to carry out live fire drills with rockets, cannons or free-fall ordinance, Mulloy said, although the government has made no mention of such drills.

The government must still obtain the approval of the community of Nishinoomote, which has nominal jurisdiction over the island and owns the remaining 1 per cent of the territory. The local government has to date been “cautious” on the issue of the island being used for military training.

Additional reporting by Kyodo