The Obama administration added the names of four Iranian companies and an individual to those sanctioned for assisting Iran's suspected nuclear weapons program.
"Iranian private sector firms should heed the risks incurred by conducting business with those who support Iran’s proscribed nuclear activities and should choose to focus their activities on legitimate international commerce," the State Department said Thursday in a statement.
"The United States will continue to investigate and research similar activities, and additional companies making material contributions to the Iranian government’s proliferation of weapons of mass destruction or their means of delivery will likely be designated," it said.
The companies named include Aluminat, alleged to have provided centrifuge components to the program; PASK, alleged to have worked with Iran's nuclear energy agency to procure vacuum equipment; Pishro, alleged to provide research and development to the nuclear program; and Taghtiran Kashan, alleged to have helped procure sensitive material for the program, including uranium containers.
Also named is Parviz Khaki, 44, alleged to have procured goods that can be used to build centrifuges and enrich uranium.
Iran says its nuclear program is for peaceful purposes.