The head of China's General Staff of the People's Liberation Army (PLA) has confirmed that China's first aircraft carrier is under construction.
Gen Chen Bingde refused to say when the carrier - a remodelled Soviet-era vessel, the Varyag - would be ready.
A member of his staff said the carrier would pose no threat to other nations.
The 300m (990ft) carrier, which is being built in the north-east port of Dalian, has been one of China's worst-kept secrets, analysts say.
Gen Chen made his comments to the Chinese-language Hong Kong Commercial Daily newspaper.
Symbol of power
The PLA - the largest army in the world - is hugely secretive about its defence programme.
The carrier was constructed in the 1980s for the Soviet navy but was never completed. When the Soviet Union collapsed, the rusting hull of the Varyag sat in dockyards in Ukraine.
A Chinese company with links to the PLA bought the Varyag claiming it wanted to turn it into a floating casino in Macau.
The carrier is thought to be nearly finished, and is expected to begin sea trials later this year.
But the BBC's Michael Bristow in Beijing says that does not mean it will then be ready to undertake operational duties.
Learning how to operate it - and fly planes off it - will take a few more years to master, our correspondent says.
Lt Gen Qi Jianguo, assistant chief of the general staff, told the Hong Kong Commercial Daily that even after the aircraft carrier was deployed, it would "definitely not sail to other countries' territorial waters".
"All of the great nations in the world own aircraft carriers - they are symbols of a great nation," he was quoted as saying.
Lt Gen Qi said China had always followed a "defensive" principle for its military strategy.
"It would have been better for us if we acted sooner in understanding the oceans and mapping out our blue-water capabilities earlier.
"We are now facing heavy pressure in the oceans whether in the South China Sea, East China Sea, Yellow Sea or the Taiwan Straits," he said.
China is engaged in maritime border disputes with several countries - including Vietnam and the Philippines.
The US, which has 11 fully-capable carrier strike groups, has also expressed concern about its rising naval ambitions.
The PLA has invested heavily in submarines. It is believed to be close to deploying the world's first "carrier-killer" ballistic missile designed to sink aircraft carriers while they are manoeuvring at sea up to 1,500km offshore, and it is building its own stealth fighter aircraft along with advanced carrier-based aircraft built from Russian designs.
All of these can target US bases, US ships and US carriers in Asia.
India is another emerging power pursuing a similar path - with an ex-Soviet carrier being modified for the Indian Navy, and work already under way on a first home-built vessel as well.
Over time, these developments will affect the maritime balance of power in Asia, says the BBC's defence and security correspondent Nick Childs.
China says other countries have nothing to fear, but its recent assertive diplomatic and military muscle-flexing has created waves in the region, he says.