The Commerce Department has issued warnings to at least 20 American companies in an effort to disrupt Russia’s war efforts in Ukraine, according to a U.S. official who spoke on Thursday. These companies are involved in the production and sale of products that have been found in missiles and drones recovered in Ukraine, despite sanctions imposed by the U.S. and other countries on Russia following its invasion in 2022.

At the department’s annual export control conference in Washington, D.C., Assistant Secretary Matthew Axelrod revealed that letters had been sent to American companies containing a list of more than 600 foreign parties. The companies were asked to voluntarily cease shipping to these parties due to the high risk of transshipment to Russia.

In addition to these measures, senior U.S. officials from the Commerce, State, and Treasury departments have been engaging with leaders of U.S. companies to explore further actions they can take to prevent their products from being used by Russia. The U.S government is urging American companies to halt the shipment of goods to more than 600 foreign parties over concerns that these items could end up being used by Russia in its invasion of Ukraine.