CANBERRA/HONG KONG, March 21 (Reuters) - The Pentagon's F-35 warplane is giving U.S. allies in Asia a headache as they look to replace ageing jets with a cutting edge aircraft now likely to be at least seven years late in offering a strategic deterrent to China.
The $400 billion weapons project has suffered technical faults, delays, cost overruns and now U.S. budget cuts that could force Washington to scale back its own purchases.
At the same time, China's soaring defence spending is rapidly eroding the advantage in technology, particularly in air power, that Washington and some of its regional allies have had over the People's Liberation Army (PLA) since the 1950s.
China is also flight testing two stealth fighters, the J-20 and the J-31, although they are not expected to enter service until the end of the decade at the earliest, military aviation experts said.
"It's an open question as to how advanced and sophisticated they actually are," said Andrew Davies, a senior strategy analyst at the Australian Strategic Policy Institute, referring to the Chinese fighters.
"But having said that, they make life more difficult for existing types, so the F-35 becomes more important."
The F-35 is the costliest weapons programme in history. Lockheed Martin Corp is the prime contractor. Pratt & Whitney, a unit of United Technologies Corp, makes the engine.
Australia has ordered 100 F-35s, although defence analysts say it might buy only 50 to 70 given Canberra is expected to decide in June to double its fleet of 24 Boeing Co F/A-18 Super Hornets. That would prevent a frontline gap until the F-35 is delivered later in the decade.
Japan said it was not changing its plan to buy 42 planes while South Korea is expected to choose the F-35 as the winner of a 60-jet competition to be decided this summer.
Singapore is likely to order more than a dozen F-35s in the coming weeks.
When Asian customers first lodged orders, regional conflict appeared remote. But a bitter territorial dispute between Beijing and Tokyo over a group of islands in the East China Sea has crystallized attention on China's expanding fleet of advanced fighters and strike aircraft.
China is also pitted against the Philippines, Vietnam and other Southeast Asian nations over claims to the South China Sea. Both bodies of water are potentially rich in oil and gas.
Western analysts are skeptical about whether the new Chinese fighters will be any match for the fifth generation F-35 or the more expensive Lockheed Martin F-22 Raptor already in service with the U.S. air force but not available for export.
In addition to the challenges of designing and operating stealth aircraft, China will have to overcome shortcomings with locally made engines that have forced it to rely almost exclusively on Russian power plants for its current frontline fighters.
While Lockheed continues to promise F-35s on Asia-Pacific runways from around 2017, the aircraft may not be available in meaningful numbers for five years beyond that.
That leaves Japan and South Korea relying on a generation of older planes the F-35 was supposed to replace.
"You can keep an aeroplane for as long as you want. The problem with aircraft age is you lose availability and reliability of the aircraft," said Australia's air force chief, Air Marshal Geoff Brown.
Japanese defence officials and experts said Tokyo was not about to panic.
"It's not like China has great stealth fighters. What matters in military capability is where you are in relation to your opponent," said Toshiyuki Shikata, a Teikyo University professor and a retired general.
Japan is not sitting on its hands. It is upgrading its fleet of about 200 Boeing F-15s, its mainstay fighter.
Tokyo has committed so far to buying only four F-35s but is building an assembly line to manufacture the remaining 38 aircraft locally.
The F-35 locks Japan in with the future U.S. order of battle - as it does for Australia, South Korea and Singapore - flying the same sensor-packed fighter aircraft as U.S. forces.
"Tensions with China will absolutely lock that in. And South Korea will follow Japan, because politically it would be very difficult for a South Korean government to be seen to settle for something less than Japan has," said Davies.
Steve O'Bryan, Lockheed's F-35 vice president for program integration, said all the world's great militaries were employing fifth generation capability for future deterrence and security needs.
"Only fifth generation aircraft give you the enhanced flexibility, versatility and the ability to deploy anywhere to meet the challenge of future emerging threats," O'Bryan said.
The F-35 could still be a rare sight in Asia.
Japan's 42 F-35s would join an air force of more than 350 fighter aircraft, some old even by fourth generation standards.
Assuming it places an order, South Korea's 60 would replace ageing types in an air force of more than 460 fighter bombers, while Singapore's handful would spearhead a force of around 148 aircraft, many of them later model F-15s and F-16s. Singapore is likely to buy additional batches of F-35s in the coming years, eventually building its fleet up to as many as 75, according to U.S. government and industry sources.
Even if all four countries opt for the plane in numbers expected by Lockheed, the F-35 will still only account for roughly one in 10 frontline aircraft in Asia, although in Australia it would be one in two.
Former U.S. Air Force Secretary Michael Wynne, a strong supporter of the F-35, is encouraging the U.S. air force to rapidly deploy its early F-35s to U.S. bases in the region, networking them with F-22s and other warplanes to send a powerful message to China and North Korea.
Chinese military planners have already gotten the message about air power, having studied the way the United States and its Western allies crushed opponents in the Balkans and the Middle East.
In these conflicts, coordinated air and missile strikes on air defence systems, communications and air-bases allowed the United States to control the skies, leaving their adversaries blind and virtually defenceless.
The PLA has set out to ensure it would not suffer this fate, military experts said.
Underpinning its defences, China has built a hardened, integrated air defence system bristling with batteries of Russian-made and locally produced surface-to-air missiles.
Since 2000, the PLA air force has taken delivery of almost 550 advanced fighter and strike aircraft that potentially match or even exceed the capabilities of all current Western aircraft except the F-22, some aviation experts said.
And, the PLA still has more than 1,000 less advanced fighters to defend its airspace.
That means only the U.S.'s 185 F-22s and 20 stealthy B-2 bombers could penetrate China's airspace in a conflict right now, according to senior U.S and Asian military commanders.
Another key objective for Beijing is to keep U.S aircraft carrier battle groups far away from areas of operations near the Chinese coast.
It has invested heavily in submarines, surface warships and missiles that could be used to attack carriers or keep them at bay, forcing their aircraft to operate at long distances.
Paradoxically, some analysts believe China's capacity to attack carriers could mean the F-35 makes less difference to Asia's arms buildup than most assume.
"It's a bit radical, but I don't think the U.S. Navy really needs the F-35 because I don't think the USN can get the F-35 within range of Chinese targets. The Chinese capacity to sink the carriers they are floating on is too great," said Hugh White, a former top Australian defence official who steered Canberra's decision to buy the F-35.