The US Treasury Department said one of the companies, Thailand-based Asian Aviation Logistics will now fall under US sanctions.
AAL, which lists its business address on Sri Nakarin Road in Suan Luang district of eastern Bangkok, is a little-known firm with no public presence. It has no web page, and its Facebook page is blank.
According to the US announcement, Asian Aviation helped the Iranian airline Mahan Air to obtain parts and material. Mahan Air was already a sanctioned company.
The US move comes as the United States and five other global powers are working with Iran to strike a comprehensive agreement under which Tehran would curb its nuclear activities in exchange for an easing of economic sanctions that have crippled its economy.
The Treasury Department said it was targeting the people and firms, including Iran's Asia Bank, Meraj Air and Lissom Marine Services LLC, a shipping firm, for a range of violations, including helping Iran's missile and nuclear programs, evading prior sanctions, or supporting terrorism.
In a parallel move, the US Department of State imposed sanctions on four firms it said were helping Iran's nuclear program, a UAE-based firm working with Iran's shipping sector, Goldentex FZE, and an Italian firm, Dettin SpA, it said was working with Iran's petrochemical industry.
"Our actions today and since the start of the (nuclear) talks are consistent with our commitments under the Joint Plan of Action, which provided limited relief of certain sanctions in exchange for Iranian steps that halted its nuclear program and rolled it back in key respects," Caitlin Hayden, spokeswoman for the National Security Council, said in a statement.
The United States and some of its allies suspect Iran is using its civilian nuclear program as a cover to develop atomic weapons. Iran denies this, saying that its program is solely for peaceful purposes.
Six major powers and Iran failed to meet a July 20 deadline to negotiate the comprehensive nuclear deal. The six, a group comprising Britain, China, France, Germany, Russia and the United States known as the P5+1, have agreed to extend the deadline to reach a comprehensive agreement until Nov 24.
The next talks are expected in mid-September.