Russia is receiving materials from Iran to build a drone factory on its territory that "could be fully operational early next year," White House national security spokesman John Kirby warned Friday.
The White House released a satellite image of the location of the prospective plant in the Alabuga special economic zone, some 900 kilometers (560 miles) east of Moscow.
"The Russia-Iran military partnership appears to be deepening," Kirby said in a statement, citing US intelligence information.
The White House said it would release a new government advisory to assist businesses and governments "to ensure they are not inadvertently contributing to Iran's (drone) program."
Washington estimates that Russia has received hundreds of attack drones as well as related equipment from Iran to aid Moscow's invasion of Ukraine.
According to US data, the drones are built in Iran, shipped across the Caspian Sea "and then used operationally by Russian forces against Ukraine," Kirby said.
The White House published a map depicting the purported delivery route from the Iranian city of Amirabad, to Makhachkala in southern Russia, from which the drones are then transported to an airbase in Primorsko-Akhtarsk on the Azov sea.
"Russia has been using Iranian UAVs in recent weeks to strike Kyiv and terrorize the Ukrainian population," Kirby added, referring to unmanned aerial vehicles, or drones.
Washington sounded the alarm on what it says are Moscow's efforts to begin manufacturing Iranian drones itself.
"We have information that Russia is receiving materials from Iran needed to build a UAV manufacturing plant inside Russia," Kirby said.
In turn, Iran is seeking to purchase Su-35 fighter jets, attack helicopters, radars, and YAK-130 combat trainer aircraft from Russia worth billions of dollars, according to the White House.
"We will continue to impose sanctions on the actors involved in the transfer of Iranian military equipment to Russia for use in Ukraine," Kirby said.
Iran has repeatedly denied US accusations of sending military supplies to Russia during its war against Ukraine, now into its second year.
The war has revived cooperation between Moscow and Tehran, both facing growing international isolation.
The two countries recently announced the construction of a rail link aimed at circumventing traditional sea routes and international sanctions.