The United States has formally labelled Iran’s Islamic Revolutionary Guard Corps a terrorist organization.
Iran immediately condemned the decision.
Tensions between the two countries have grown since 2015.
The United States pulled out of a nuclear deal with Tehran last May and reimposed sanctions that crippled Iran’s economy.
Trump said the accord did not address Iran’s ballistic missile activity.
He said, the IRGC is the Iranian government’s primary means of directing and implementing its global terrorist campaign and influence in the region.
The step raises the specter of retaliation from Tehran in an increasingly tense Middle East.
The IRGC was set up after the 1979 Islamic Revolution and has a huge influence in the Iranian political system.
Controlling large swathes of the economy and the armed forces, its mission is to protect the Shi’ite clerical ruling system.
The IRGC’s involvement in Iran’s banking and shipping industries could complicate matters with U.S. allies including the European Union.
Trump said, doing business with the IRGC will be bankrolling terrorism.