The Wall Street Journal reports that Moscow and Tehran are cooperating on plans to construct a new factory in Russia that could make at least 6,000 Iranian-designed drones to be used in the war on Ukraine.

The WSJ quoted officials from a country aligned with the US as saying that a high-level Iranian delegation traveled to Russia in early January to visit the site for the factory and decide on details to kick off the project.

The Iranian delegation was reportedly led by both sanctioned Brigadier Geneneral Abdollah Mehrabi, head of the Islamic Revolutionary Guard Corps Aerospace Force Research and Self-Sufficiency Jihad Organization, and Ghassem Damavandian, the chief executive of Iran’s Quds Aviation Industry.

The Islamic Republic has already provided Russia with hundreds of drones it has used to hit military and civilian targets in Ukraine.

The officials say the drone factory is part of a $1 billion deal between the two allies. Moscow has provided Iran with weapons seized on the battlefield in Ukraine that they are trying to reverse engineer, the officials added.

The Biden administration has warned that Russia and Iran are developing a “full-fledged defense partnership.” The White House says Moscow was training Iranian pilots to fly Russian jet fighters, with the intent of providing Tehran with the fighters by year’s end.