Russia is shipping advanced fighters to China, possibly to better arm its strategic partner against the U.S.

Chinese and Russian officials revealed at this week’s China International Aviation and Aerospace Exhibition in Zhuhai, Guangdong that a shipment of four Russian Sukhoi Su-35 Flanker-E fighters will be delivered to the Chinese People’s Liberation Army (PLA) before the year’s end, reports the Financial Times.

In accordance with the obligations of a $2 billion contract signed in November 2015, Moscow will give Beijing 24 Su-35s over the next three years.

Russia informally banned the sale of advanced weapons to China in 2004, noting concerns over the replication of Russian technology. China has traditionally built up its military by reverse engineering and cloning foreign technology. During the 1990s and early 2000s, China acquired a significant amount of advanced technology, such as the Su-27 multi-role fighter, T-90 tank, and key submarine components, from Russia. China incorporated parts of the Su-27 into its J-10 fighter. Aspects of previous versions of Russia’s Flanker aircraft were added into China’s J-11, J-15, and J-16 aircraft.

The Su-35 is Russia’s most advanced fighter jet, and it has been hesitant to sell its prized plane to China. Powerful countries typically do not sell off their top weapons systems to rising powerhouses with the ability to threaten their strategic interests. But, Russia is not only selling its Su-35. It will also provide S-400 surface-to-air missile systems to China. The SAM system is expected to arrive in 2018 in accordance with a 2014 agreement. Russia and China have $8 billion wrapped up in various defense contracts.

Why is Russia suddenly willing to hand over its advanced weapons? There are two possible reasons.

One, cash-strapped Russia needs the money. International sanctions are crippling the Russian economy, and selling weapons to China is an easy way to bring in much-needed funding. China spent $215 billion on defense last year. With that kind of budget, China is an excellent market for arms sales. The Chinese are among the top five importers of Russian weapons.

Two, Russia is strengthening its informal alliance with China as both powers attempt to challenge U.S. primacy.

“Given Russia’s current practice of doing whatever it can to complicate the strategic planning of the US and its allies, it is not surprising that Russia would be prepared to release some of its advanced weaponry to China,” Australian security analyst Allan Behm told the Financial Times. Tensions between the U.S. and China have risen in response to Chinese objections to America’s strategic rebalance to Asia, specifically its increased military involvement in the South China Sea.

The Su-35 will greatly enhance China’s air defense capabilities as it strives to counter U.S. air power in Asia. The Su-35 is an extremely capable aircraft with the ability to rival America’s fourth-generation fighters.

China recently presented its J-20 fighter as a breakthrough in Chinese stealth fighter technology and an essential component for power projection and the emergence of China as a Pacific power, but if the J-20 was as ready for combat as Chinese media suggests, China would not need to purchase Su-35s from Russia. Chinese jet engines are vastly inferior to Russian engines, and China will likely attempt to harvest this technology from the new Su-35s and use it to boost their “independent” defense systems.

Although Russia has demonstrated a willingness to once again provide advanced arms to China, there are still certain weapons it refuses to sell, such as the Iskander cruise missile and satellite systems for the detection of ballistic missile launches.

Follow Ryan on Twitter

Send tips to ryan@ dailycallernewsfoundation.org.

Content created by The Daily Caller News Foundation is available without charge to any eligible news publisher that can provide a large audience. For licensing opportunities of our original content, please contact licensing@dailycallernewsfoundation.org.