(Bloomberg) -- China is providing Russia with significant quantities of components to build cruise missiles and drones as well as optical parts for tanks and armored vehicles, allowing Moscow to ramp up defense production in its war against Ukraine, senior US officials said.

The White House is urging Chinese firms to cease their support and encouraging European allies to put pressure on Beijing to end sales from companies like Wuhan Global Sensor Technology Co., Wuhan Tongsheng Technology Co. Ltd., and Hikvision that are providing critical components for Russian military systems, according to an official who briefed reporters on condition of anonymity Friday.

While there is no evidence China is providing lethal assistance, people familiar with the US intelligence assessment characterized the aid as just as significant, saying that without the imports, Russia’s military industrial base would struggle.

Chinese officials argue the country isn’t taking a side in the face of Russia’s full-scale war, even as Chinese President Xi Jinping and Russian President Vladimir Putin have established a deep alliance. For well over a year, China has pushed back on US claims that it has considered providing lethal aid to Russia in its war, saying it never sells arms to parties involved in a conflict. Chinese officials have also noted that some technology is dual-use, with both commercial and military applications. 

But one person familiar with US intelligence described a ramping up of Chinese support for Russia. 

The assistance from Chinese firms detailed Friday likely includes nitrocellulose which Russia uses to make propellants for weapons, according to the officials. They also said Chinese entities are working to produce drones within Russia, according to intelligence gathered by the US. The underlying intelligence materials were not provided by individuals who described the conclusions.

In the last quarter of 2023, 70% of Russia’s machine tools and 90% of its microelectronics imports came from China, the official said, material which Russia has used to produce missiles, tanks and aircraft. The companies providing machine tools include Dalian Machine Tool Group, a leading manufacturer, according to the officials.

Russia has also received military optics that are manufactured by Chinese firms “iRay Technology” and North China Research Institute of Electro-Optics for use in tanks and armored vehicles, according to the officials.

The officials provided no other details on iRay Technology. Shanghai-listed iRay Technology Co. denied any involvement in military business, saying in an email that it provides X-ray imaging systems for medical, dental and other commercial use, and has never manufactured or provided any products used in tanks or armored vehicles.

The push comes as US intelligence has seen Russia dramatically ramp up production of military equipment with its invasion of Ukraine now in its third year, and as Kyiv struggles to defend its territory with weapons supplies dwindling. Further US assistance has been tied up in Congress, leading administration officials to warn the situation for Ukraine is increasingly dire.

Read more: Russian Attacks on Ukraine Stoke Fears Army Near Breaking Point 

Russia has been paying China for the support it receives, and banks handling those payments are effectively supporting Russia’s military and could be subject to US sanctions, according to the person familiar. It was previously reported the US concluded China provides Russia satellite imagery for military purposes, as well as machine tools for tanks, propellants to be used in missiles and other materials.

Earlier: China Providing Geospatial Intelligence to Russia, US Warns

President Joe Biden’s administration has sought to crack down on firms that are helping Russia evade sanctions that the US and allies imposed on Moscow after it invaded Ukraine in 2022. The US has raised their concerns with China, including on a recent call between Biden and Xi and at a summit between the leaders last year.

US Treasury Secretary Janet Yellen warned this month that any companies that provide material support for Russia’s war will face significant consequences and banks that facilitate significant transactions “expose themselves to the risk of US sanctions,” after talks in China.

The US sanctions office is investigating several companies involved in shipments of chips that ultimately end up in Russia, including from some produced by US-headquartered microelectronics manufacturers.

(Corrects to remove link to iRay Technology Co., adds company response)

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