China’s first aircraft carrier embarked on its inaugural sea trial yesterday, Beijing said, a move likely to stoke concerns about the nation’s military expansion and growing territorial assertiveness.

Beijing only recently confirmed it was revamping an old Soviet ship to be its first carrier and has sought to play down the vessel’s capability, saying it will mainly be used for training and “research”.

The US said it would like China to explain why it needs an aircraft carrier amid broader US concerns about Beijing’s lack of transparency over its military aims.

“We would welcome any kind of explanation that China would like to give for needing this kind of equipment,” State Department spokes­man Victoria Nuland told reporters when asked whether the carrier would raise regional tensions.

“This is part of our larger concern that China is not as transparent as other countries. It’s not as transparent as the US about its military acquisitions, about its military budget,” she said.

“And we’d like to have the kind of open, transparent relationship in military-to-military affairs,” Ms Nuland said.

“In our military-to-military relations with many countries around the world, we have the kind of bilateral dialogue where we can get quite specific about the equipment that we have and its intended purposes and its intended movements,” she said.

The aircraft carrier’s voyage comes amid heightened tensions over a number of maritime territorial disputes involving China, notably in the South China Sea, which is believed to be rich in oil and gas and is claimed by several countries.

The defence ministry said the carrier’s first sailing would be brief, and that the ship would afterwards return to the northeastern port of Dalian for more “refit and test work”.

Andrei Chang, head of the Kanwa Information Centre, which monitors China’s military, said it would probably test whether the engines worked, and that on-off sea trials were likely to continue for another year or two.

China’s People’s Liberation Army – the largest armed force in the world – is extremely secretive about its defence programmes, which benefit from a huge and expanding military budget boosted by the nation’s runaway economic growth.

Earlier this year, China announced military spending would rise 12.7 per cent to 601.1 billion yuan ($91.7 billion) in 2011.

In January it revealed it was developing its first stealth fighter jet, and it is also working on an anti-ballistic missile capable of piercing the defences of even the most sturdy US naval ships.

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