Russia's invasion of Ukraine is likely to threaten one of China's most discreet but important strategic relationships in recent years: its use of Ukraine as a source of technology for the expanding Chinese military.
Military analysts and diplomats say that although the Ukraine-China link has come under increased pressure from the United States, the current conflict could largely scupper a trade that has helped China's military modernise over the last two decades.
Ukrainian frustration over Beijing's growing ties with Moscow and uncertainty over the shape of its post-war economy and government could threaten the relationship, they say.
"It's always been a good hunting ground for Chinese military technicians. There is a lot there, and it has been in some cases easier to get than getting it from Russia," said Moscow-based Chinese military analyst Vasily Kashin of HSE University.
"The relationship as it was will be completely destroyed," he said, noting Ukrainian government anger at China's diplomatic support for Russia amid other post-war uncertainties.
Beyond the high-profile acquisitions of the partially built hulk of one of the Soviet Union's last aircraft carriers and the airframe of a carrier-capable Su-33 fighter jet, China has purchased engines for its training aircraft, destroyers and tanks as well transport aircraft, according to arms transfers tracked by the independent Stockholm International Peace Research Institute.
Asia-based military attaches say, less visibly, Ukraine has long been suspected to be a source of some command-and-control systems and other technology used in missiles. Ukrainian technicians have worked on a private basis inside China.
This work is expected to continue even if the official relationship sours or becomes difficult, they said.
"One traditional advantage for China in Ukraine is generally the security situation is more fluid than Russia, so it is possible to do things unofficially," one envoy said.
China's Ministry of Defense did not respond to a request for comment.
The SIPRI data does not put a value on every deal it lists, but based on figures provided over the last decade, China has on an annual basis spent at least between $70 million-$80 million.
Long-running programmes include a $317 million-$319 million deal to provide amphibious assault vehicles and $380 million for turbofan engines for Chinese JL-10 combat aircraft trainers, the SIPRI data shows.
Another important deal was the sale of 30 gas turbines for 15 Type-052D destroyers - engines that China is now producing under license and may have also adapted and improved for more modern ships, envoys say.
To be sure, the technology China's military technicians and engineers have acquired has enabled the growth of the country's own indigenous design and manufacturing abilities, making it less reliant on Ukraine than it once was.
"China was very dependent on Ukrainian technology in the 1990s and early 2000s, but that has diminished more and more, particularly as China has developed its own design and manufacturing capabilities," said Siemon Wezeman, a senior arms transfer researcher with SIPRI.
"There still may be some technology the Chinese are after, particularly aerospace and missile related… and traditionally they (Ukraine) produce quality, it is cutting edge," Wezeman told Reuters.
Russia remains China's most important source of military technology, but Ukraine has provided some items that Moscow can be reluctant or slow to give, reflecting its Soviet-era role as a military shipbuilding and aerospace hub.
SIPRI data shows a significantly larger Russia-China trade, encompassing more advanced turbofan engines for its aircraft, radars and advanced surface-to-air, anti-ship and anti-tank missiles as well as naval guns and transport aircraft.
But a habitually suspicious Moscow has not always provided its latest technology to its large neighbour, the envoys say. As an example, China's rival South China Sea claimant Vietnam was able to obtain far more advanced Kilo diesel electric submarines from Russia over the last decade.
"My guess is that Ukraine for some years filled an important niche for China, in that it might have easier to get certain products and technologies that Russian might have been less keen to sell them," said Singapore-based strategic consultant Alexander Neill. "But China's own indigenous design and manufacturing capacities have improved and to a large extent Ukraine has probably served its purpose."
Any intensifying U.S. involvement in post-war Ukraine could also complicate the trade.
Already, pressure from Washington has had an impact. The Ukrainian government confirmed last year that it would halt the takeover of local aircraft engine maker Motor Sich by Chinese aerospace company Skyrizon due to U.S. concerns of forced technology transfers.
(Reporting By Greg Torode. Editing by Gerry Doyle)
