The PLA's first two generations - the Han class and the Shang class - were considered far from perfect despite the input of Russian technology.

'Even if a modern submarine is almost silent, that is still too noisy,' said one retired Western submariner with experience in Asian waters. 'Operational stealth is everything ... and when the Type 095 is launched, all eyes and ears will be looking to see if the PLA has finally reached the standards of US, French, British and Russian nuclear subs.'

Just when the Type 095 is ready for launching is far from clear. The reference in the latest report surprised some analysts, coming after several years of speculation that has yet to yield open evidence of such a vessel nearing completion or even under construction.

'Many of us were surprised to see this submarine mentioned, as there has been no sign of progress,' said one Asian military attach?.

'If the Pentagon has something fresh, there is no sign of it in the report, and they've been keeping it to themselves.'

Both Chinese and foreign analysts note that the PLA's submarine programme is traditionally one of its most secretive, even more so than its much-vaunted missile development.

US military officials providing background briefings on the report provided no extra details, saying only that China appeared to be building a fleet with a range of capabilities, from its large Jin-class nuclear-powered missile submarines, capable of launching a nuclear ballistic missile at sea, to smaller but stealthier diesel-electric submarines. The report noted that five Jin-class submarines - expected to be based at the South Sea Fleet's new underground submarine base near Sanya , Hainan - are expected to be in operation soon.

Google Earth images surfaced last week purporting to show the Huludao shipyard in Liaoning back in March, the traditional home of PLA nuclear submarine construction. Only two Jin-class submarines are visible.

China has been steadily modernising its ageing, obsolete fleet and, with 60-odd vessels already operating, will soon have more submarines than the US. But the US is expected to hold the edge for many years when submarine technology, stealth and operational capabilities are considered. Japan has a significantly smaller fleet, but its vessels are considered to be exceptionally silent.

'There is more to submarines than just numbers,' said William Murray, a retired submariner and associate research professor at the US Naval War College. 'You have to remember that the best submarines out there now are impossible to find... China may indeed get there at some point, but in terms of the technology required, there is no substitute for time, money and experience.

'It might well be the case that when Type 095 is finally launched, further generations will still be needed to catch up on the stealth of other nations' submarines, however excited Chinese netizens get.'

He added, however, that the scale and apparent success of China's expanded ballistic and cruise missile programmes showed that, in a military context, industries were capable of fast technological expansion.

Gary Li, a PLA analyst at the International Institute of Strategic Studies in London, said previous 'new generation' submarines had generally delivered updates and tweaks of existing designs rather than creating entirely new vessels. 'The big question is when the Type 095 will be ready ... and there is nothing out there yet to suggest it will be soon,' he said.

Even so, the prospects of both the Jin and Type 095 classes in operation across the western Pacific are being noted by planners at the Pentagon, who must cope with budget cuts for years to come.

The latest report says, for example, that the endurance of China's nuclear-powered ballistic missile and attack submarines will significantly extend the reach of the PLA navy beyond a Taiwan invasion scenario.

Wary of weapons that seek to deny US warships access to areas that cover traditional allies such as Japan, South Korea and even Australia, Pentagon strategists are increasing deployments in the region.

They are also seeking to work more closely with allies, who are also expanding submarine fleets, on joint patrols and anti-submarine warfare operations, considered a long neglected military craft.

China is expected to pay close attention to joint US-South Korean anti-submarine drills planned for next month in the Yellow Sea.

Ocean force

The PLA Navy has the largest force of principal combatants, amphibious and warfare ships in Asia

Destroyers: 25

Frigates: 49

Tank landing ships/ amphibious transport docks:27

Medium landing ships: 28

Diesel attack submarines: 54

Nuclear attack submarines: 6

Coastal patrol (missile): 85

Total: 274