A news website run by China's defence ministry said Thursday the nation's aircraft carrier should handle territorial disputes, despite government assurances the vessel posed no threat to its neighbours.

The comments came a day after the 300-metre (990-foot) vessel embarked on its maiden sea trial, prompting a worried United States to demand China explain why it needs an aircraft carrier, amid concerns over Beijing's military aims.

China has repeatedly insisted the carrier -- an old Soviet ship that is being refitted in the northeast of the country -- will be used mainly for training and research, and does not change Beijing's defensive military policy.

But in a comment piece published on jz.chinamil.com.cn, Guo Jianyue, a senior reporter at the top state-run military newspaper PLA Daily, said the carrier should be brought out for disputes. The website is an offshoot of the main PLA Daily site.

"Why did we build it if we don't have the courage and willingness to use the aircraft carrier to handle territorial disputes?" he asked in the article.

"It is reasonable to use the aircraft carrier or other warships to handle disputes if there is any need.

"The reason why we built a carrier is to safeguard China's maritime rights and interests more efficiently. We will be more confident and have more determination to defend our territorial integrity after we have carriers."

China's state-run newspapers and websites are carefully edited, which indicates the comment piece received approval at a higher level, although it may not necessarily reflect the general consensus.

On Wednesday, US State Department spokeswoman Victoria Nuland said Washington "would welcome any kind of explanation that China would like to give for this kind of equipment."

"This is part of our larger concern that China is not as transparent as other countries. It's not as transparent as the United States about its military acquisitions, about its military budget," she said.

Other countries have in the past also voiced similar concerns, as China's military expands and the Asian nation grows more assertive about its territorial claims, notably in the East China Sea and South China Sea.

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.