The U.S. Treasury Department has targeted a series of Iranian charitable trusts connected to the country's Revolutionary Guard Corps and its national shipping lines in the latest round of designations aimed at thwarting Iran's nuclear weapons program.

The trusts, called bonyads, receive government support but disclose little about their operations. The actions came under a presidential order targeting the assets of people involved with weapons of mass destruction.

The newly designated groups are "major institutional participants in Iran's illicit conduct and in its attempts to evade sanctions," Treasury Under Secretary for Terrorism and Financial Intelligence Stuart Levey said in a statement issued Tuesday. Among the Iranian entities targeted is the Moallem Insurance Company for providing insurance to the shipping lines. The Liner Transport Kish also was designated for helping send weapons to Hizballah for the Revolutionary Guard, or IRGC.​

"The IRGC continues to be a primary focus of U.S. and international sanctions against Iran because of the central role it plays in Iran's missile and nuclear programs, its support for terrorism, as well as its involvement in serious human rights abuses," the Treasury statement said.

Officials insist the U.S.'s widening sanctions program is being felt within Iran, but has yet to bring about the desired effect of persuading the government to back away from developing nuclear weapons.