WASHINGTON (AP) — The United States said Tuesday it is imposing a new round of sanctions on Iranian firms and people accused of procuring equipment used for Iranian drones.

Treasury’s Office of Foreign Assets Control coordinated with the FBI to designate four firms and three people in Iran and Turkey for allegedly buying equipment, including European-made engines, to be used for Iran’s drone and weapons programs.

Those targeted for sanctions include the Iran-based Defense Technology and Science Research Center, its procurement firm Farazan Industrial Engineering Inc. and two other firms along with purchasing agents from the companies.

“Iran’s well-documented proliferation of UAVs and conventional weapons to its proxies continues to undermine both regional security and global stability,” said Brian Nelson, Treasury's undersecretary for terrorism and financial intelligence. Nelson was referring to unmanned aerial vehicles.

“The United States will continue to expose foreign procurement networks in any jurisdiction that supports Iran’s military industrial complex," he said.

American defense officials say Iran is supplying Russia with unmanned drones to use on civilians as the Kremlin presses its invasion of Ukraine, which has entered its second year.

Among other things, sanctions deny the people and firms access to any property or financial assets held in the United States and prevent American firms and companies from doing business with them.

Tensions between the U.S. and Iran have worsened after months of antigovernment protests.