The United States imposed new sanctions Iran on Tuesday, targeting the Islamic republic's Revolutionary Guard and its energy and shipping sectors over Tehran's nuclear and weapons activities.
Sanctions were placed on entities linked to the guards corp, which is seen as a key driver of Iran's suspected nuclear weapons program.
Those targeted included guards member Parviz Fattah, a former energy minister, as well as a raft of financial firms.
The Treasury Department also hit Iran's economically vital energy sector, sanctioning the Pars Oil and Gas Company, which is responsible for tapping some of the world's largest gas fields.
The North and South Pars fields are a potential economic lifeline for the sanctions-hit nation, but leaders in Tehran have struggled to finance operations amid sanctions.
The development of the fields has been hampered by a lack of investment and technology as Western firms either have pulled out or delayed their commitments.
Iran, the second largest oil exporter in the Organization of Petroleum Exporting Countries (OPEC) also has the world's second largest natural gas reserves after Russia.
The United Nations, the United States and the European Union recently imposed new punitive measures against Tehran in a bid to stop its sensitive uranium enrichment program which they fear masks a weapons drive.
Tehran denies the charge, saying the program has purely peaceful goals.
The Treasury Department also sanctioned Liner Transport Kish, for "providing material support, including weapons to Hezbollah" on behalf of the guards.
The Islamic Revolutionary Guard Corps and Islamic Republic of Iran Shipping Lines are both "major institutional participants in Iran's illicit conduct and in its attempts to evade sanctions," said US sanctions tzar Stuart Levey.
"We will therefore continue to target and expose their networks," he said.