The U.S. has been uncovering increasing evidence that China is a major, and discreet, supplier of military technology to Iran. Evidence of Chinese tech is showing up in Iranian missiles, and their nuclear weapons program. China is believed to have helped Iran develop the tricky technology to build large solid fuel rocket motors. For example, last year Iran conducted another successful test of its long range (2,000+ kilometers) solid fuel ballistic missile (the Sejil II). Solid fuel missiles can be launched without preparation. This is critical, as the liquid fueled missiles take hours to prepare for launch, and spy satellites pass over Iran frequently enough to spot this. Iran is believed to have over a hundred older, liquid fueled missiles, and production of these will apparently cease because of the success of the new solid fuel motors. But in the meantime, Iran continues to build silos for its long range liquid fuel rockets, so they can be prepared for firing (fueled) without that being detected by satellites.
The Sejil IIs can reach Israel, and Iran is known to be working towards a longer range missile that can reach Europe. Two years ago, Iran tested a new IRBM (Intermediate Range Ballistic Missile) called the Sejil. This was a solid fuel missile. Three years ago, Iran had a failed test of a solid fuel ballistic missile it called "Ashura." The Sajil appeared to be the Ashura with a new name, and modifications that make it work. Even then, the big question was, who did they get the solid fuel manufacturing technology from? There are many potential vendors (North Korea, Pakistan, Russia, China, or even stolen from the West). China, it appears, is the most likely donor. Iran has been manufacturing solid fuel for smaller rockets for over a decade, but had not yet developed the technology to build larger, and reliable, solid fuel rocket motors.
For the last five years, Iran has been producing Shahab 3 IRBMs. This missile is basically 1960s technology, with the addition of GPS guidance. Russian and North Korean missile technology has been obtained to make the Shahab 3 work. This has resulted in a missile that apparently will function properly about 80 percent of the time, and deliver a warhead of about one ton, to a range of some 1,700 kilometers, to within a hundred meters of where it was aimed. By world standards, this is a pretty effective weapon. A solid fuel version of this missile would be, if the solid fuel was of reasonable quality, about ten percent more reliable than liquid fuel, and easier to hide and launch.
A more obvious sign of Chinese cooperation occurred when, earlier this year, Iran announced that it had, in response to Russia's refusal to deliver S-300 air defense missiles, designed its own, which will have similar capabilities. How would they do that? Last year, Iran sought to purchase the Chinese made HQ-9 anti-aircraft missile system. China buys a lot of oil from Iran, and is considered an ally. China is believed to have secretly supplied Iran with a lot of military technology, including data on how to manufacture HQ-9 systems. By not delivering actual weapons, China avoids a confrontation with angry Western nations. China could deliver HQ-9 systems, but not in the usual way. A memory stick drive would do it.
China has been offering its HQ-9 system to foreign customers, as the FD-2000, for several years now. The Russians are not happy with this, given the amount of stolen S-300 technology believed to be in the HQ-9. Russia has been pointed in warning China not to export weapons containing stolen Russian tech. But the Chinese have done it, apparently believing there's really nothing the Russians can do about it. China, in this case, may have followed past practice and quietly sold Iran the technology for the FD-2000, and let them build their own, and call it whatever they want.
A decade ago, China began equipping army and navy (on ships) units with the HQ-9. Over a decade of development was believed to have benefitted from data stolen from similar American and Russian systems. The HQ-9 missile is similar to the U.S. "Patriot," while the radar apparently derived much technology from that used in the Russian S-300 system. The HQ-9 missile has a max range of about 100 kilometers, weighs 1.3 tons and has a passive (no broadcasting) seeker in the missile. A Chinese HQ-9 brigades consist of a brigade headquarters (with a command vehicle, and four trucks for communications and maintenance), and six battalions (each with a missile control vehicle, a targeting radar vehicle, a search radar vehicle and eight missile-launch-vehicles, each carrying four missiles in containers).
Neither the S-300 or HQ-9 have been tested in combat. Most earlier Russian designed air defense systems performed poorly in combat. Even the Russian SA-6 missile systems, that Egypt used in 1973, which were initially a surprise to the Israelis, were soon countered, and did not stop the Israelis from getting through. While the best sales technique is to push the products track record, you have to do just the opposite with Russian anti-aircraft missiles. Thus the Russians, and now the Chinese with their FD-2000, emphasize low price, impressive specifications, good test results and potential.
Iranian progress with their nuclear weapons program also seems to be benefiting from technology transfers. Russia is not keen to see nearby Iran equipped with nukes, especially since the Islamic radical rulers of Iran have been friendly towards Islamic militants operating inside Russia. China, on the other hand, doesn't care if Iran and Russia resume their ancient rivalry. Meanwhile, China continues to steal technology, and sell some of it, while loudly denying any such behavior. But there is a growing body of evidence against China, and this doesn't bother China much at all. They deny everything, secure in the knowledge that there's nothing anyone can do about it.