The United States has announced new sanctions against Iran-affiliated individuals and businesses over what it claims is an illicit banking network used to hide transactions.

The Treasury Department said Thursday that it has imposed sanctions on 39 firms linked to a shadow banking system that helps to conceal financial activity between sanctioned Iranian firms and their foreign buyers, including those who purchase Iranian petrochemicals.

The sanctioned companies range from Hong Kong to the United Arab Emirates, and they are intended to impede Iran’s efforts to conduct business with foreign customers.

“Today’s action demonstrates the United States’ commitment to enforcing our sanctions and our ability to disrupt Iran’s foreign financial networks, which it uses to launder funds,” said Treasury Deputy Secretary Wally Adeyemo.

Secretary of State Antony Blinken vowed the U.S. “will continue to disrupt attempts to evade U.S. sanctions.”

The new sanctions also target a network of Chinese companies and an individual accused of supplying thousands of drone components to Iran. Iran is alleged to have supplied Russia with drones used to bomb Ukrainian civilians in the nation’s invasion of Ukraine.

The sanctions deny individuals and companies access to any property or financial assets held in the United States and prohibit U.S. firms and citizens from conducting business with them.