Iran maintains that the purposes of its nuclear programme are peaceful
The US has imposed sanctions on an Iranian shipping company and 18 of its affiliates over its alleged support for Tehran's nuclear programme.
The Islamic Republic of Iran Shipping Lines (IRISL) had provided logistical support for the Iranian defence ministry, the US treasury said.
IRISL's US-based assets would be frozen and its transactions banned, it said.
The US has already imposed a number of sanctions on Iran linked to its controversial nuclear programme.
Western nations accuse Iran of seeking to develop a nuclear weapon. But Tehran says its nuclear activities are aimed solely at peaceful energy development.
The US treasury accused IRISL, a global operator, of shipping "military-related cargo" and lying about its activities.
"Not only does IRISL facilitate the transport of cargo for UN-designated proliferators, it also falsifies documents and uses deceptive schemes to shroud its involvement in illicit commerce," Stuart Levey, Under Secretary for Terrorism and Financial Intelligence, said in a statement.
"IRISL's actions are part of a broader pattern of deception and fabrication that Iran uses to advance its nuclear and missile programs," he said.
The move means that US citizens and companies will not be allowed to do business with IRISL and its affiliates. The companies' bank accounts will be frozen.
The UN has passed three rounds of sanctions against Iran aimed at curtailing its nuclear programme.
Last month, the European Union approved new measures against Tehran after it missed a deadline to respond to a proposal from the five permanent members of the UN Security Council and Germany to suspend uranium enrichment.