An Iranian drone shot down in Ukraine last year was found to contain parts made by 13 US companies, according to a Ukrainian intelligence report obtained by CNN.
Of the 52 components of the Iranian-made Shahed-136 "suicide drone”, the report found 40 had been manufactured by US businesses.
The assessment claims the remaining 12 were built by companies in Canada, Switzerland, Japan, Taiwan and China.
Russia is believed to have exhausted its Shahed-136 stockpile in November after sending an estimated 400 into Ukraine.
The long-range unmanned aerial vehicle can strike targets more than 2,000km away, Iran claims. It is propeller driven — giving it a speed of about 185kph — and is guided by GPS for accuracy.
Ukraine's military spokesman Yuriy Ignat says the country's air force has studied the drone and that its real range is probably closer to 1,000km.
Analysts at the US Foundation for the Defence of Democracy, a think tank, say this still gives Russia the option of using Belarus as a relative safe haven for launching the low-cost weapons into Ukraine.
The damage they can cause is immense: Previous attacks on critical infrastructure such as power stations have plunged millions of Ukrainians into darkness and left many without heating, as temperatures drop below zero.
Attacks on Ukraine's infrastructure have damaged or destroyed about 40 per cent of the country's power generation capacity of 58 gigawatts.
The US is looking at ways to curb Iranian drone production through sanctions and export controls, and is talking to private companies whose parts have been used in production, the White House said on Wednesday.
“We are assessing further steps we can take in terms of export controls to restrict Iran’s access to technologies used in drones,” White House National Security Council spokeswoman Adrienne Watson said.
The US had previously imposed sanctions on companies and people it accused of producing or transferring Iranian drones that Russia has used to attack civilian infrastructure in Ukraine.
Ukrainian President Volodymyr Zelenskyy claimed Moscow plans to step up the use of Iranian-made exploding drones.
“We have information that Russia is planning a prolonged attack by Shaheds,” he said on Monday.
Mr Zelenskyy said Russia's goal is to break Ukraine’s resistance by “exhausting our people, air defence, our energy”.
Ukraine, he said, had to “act and do everything so that the terrorists' fail in their aim, as all their others have failed”.
An old challenge
Think tanks and international weapons-monitoring companies say hundreds of western-made components have found their way not only into Iranian drones, but also Russian weaponry used in the Ukraine war, including the Orlan-10 drone.
In August, UK think tank Rusi released a report on foreign components used in Russian systems, including drones, saying that 450 of the components had been supplied by western companies.
The report stated that many of the companies were unaware they were providing critical parts for guidance systems, cameras and sensors.
Last month, it was discovered that Canadian company Tallysman Wireless had supplied components for the Shahed-136, though the company's chief executive said that it was not always possible to know where products were ending up.
Gyles Panther told Canada’s Globe and Mail that his company supported Ukraine and it would take action to tighten controls over re-exports.
Canadian Prime Minister Justin Trudeau warned of tougher action to control supply chains.
“We have strict export permits in place for sensitive technology that are rigorously enforced, and that’s why we will be following up with this company that is fully co-operating to try to figure out exactly how items that were not supposed to get into the hands of anyone like the Iranian government actually ended up there,” Mr Trudeau said at the time.
Ukrainian researchers also found components in the drones from Japan’s Panasonic and a company called HITEC USA.
The challenge of stopping western components from being used in Iranian military equipment is not new.
In 2019, investigators accused Czech and German companies of supplying Iranian drones with components after wreckage of an unmanned aircraft was found at Abqaiq and Kurais in Saudi Arabia, where oil facilities had reportedly been attacked by Yemen's Houthi rebels.
Many of the components found in the weapons were originally made for civilian use, as is the case with Iran's microchip supply line from the West.
A Czech report on the issue said the incident showed “the risks associated with re-exports”.
More recently, an international investigation has been working to discover how Iran was able to procure Rotax engines used in their Mohajer-6 drones, which have also been used in Ukraine.
Re-exports of engines made by Rotax, a subsidiary of Bombardier Recreational Products, are being investigated by authorities in Canada, the UK and Norway.
Stopping the re-export of microchips will be far harder, due to their ubiquity and the fact that many are “dual use” devices that have legitimate civilian purposes.
Agencies contributed to this report