Japanese troops will take part in a major US-Australian military exercise for the first time in July, as Washington looks to bolster links among its allies in the face of an increasingly assertive China.

Japan's Ground Self-Defense Force (JGSDF) -- its army -- will send 40 personnel to participate in Talisman Sabre, a two-yearly drill that begins on July 7, which will involve around 27,000 servicemen, a spokesman told AFP.

"We will participate in joint exercises with the US Marines, rather than operating directly with the Australian military," he said.

"But our participation is seen as part of efforts" to strengthen defence ties between Japan and Australia, he added.

The drill, which takes place in Australia, is intended "to improve tactical expertise in amphibian operations and to strengthen Japan-US interoperability," an army statement said.

News of Japan's participation came as tensions remain high in the region, with increasing criticism of China's behaviour in the South China Sea, where it has accelerated building artificial islands in disputed waters.

The United States is weighing sending warships and surveillance aircraft within 12 nautical miles -- the normal territorial zone around natural land -- of the reclaimed reefs.

Such a deployment could lead to a standoff in a stretch of water traversed by vital global shipping lanes.

Beijing regards almost the whole of the South China Sea as its own, and satellite images show it is rapidly building an airstrip on an artificial island in the Spratly archipelago, which is also claimed in whole or part by US ally the Philippines, and Vietnam, among others.

China has a separate territorial dispute with Japan over the Tokyo-controlled Senkaku islands, which it knows as the Diaoyus, in the East China Sea.

Washington and Tokyo have been working to cement security ties with other like-minded countries in the region.

In July last year, the United States, India and Japan held week-long war games in the Pacific.

Known as the Malabar Exercise, the annual event usually involves India and the US, but the participation by Japan's navy was its third since 2007.