US sanctions foreign firms trading with Iran
The US has imposed sanctions against seven foreign firms which trade with Iran in breach of an existing US ban.
Venezuela's state oil company, Petroleos de Venezuela (PDVSA), is among those targeted by the measures.
Other companies include firms based in the United Arab Emirates, Israel, Singapore, Monaco and Jersey.
A US official said the sanctions would add "further pressure" on Iran to halt what the US and others believe is a nuclear weapons programme.
The affected companies include Tanker Pacific of Singapore, Ofer Brothers Group of Israel, Associated Shipbroking of Monaco, Petrochemical Commercial Company International of Jersey and Iran, the Royal Oyster Group of the United Arab Emirates and Speedy Ship of the United Arab Emirates and Iran.
"All of these companies have engaged in activities related to the supply of refined petroleum products to Iran, including the direct supply of gasoline and related products," Deputy Secretary of State James Steinberg said.
Mr Steinberg said that the sanctions were tailored to target each individual firm but, in general, would stop the companies trading with the US.
PDVSA, for example, will be barred from any US government contracts, import-export financing and export licenses for sensitive technology.
The company and its subsidiaries, will, however, be permitted to continue selling oil to the United States.
The state department said the company had delivered at least two cargoes of refined petroleum products worth some $50m (£31m) to Iran between December 2010 and March 2011.
Simultaneously, the US administration imposed separate sanctions on more than 15 people and companies in China, Iran, North Korea, Syria and elsewhere.
It said the penalties were being imposed for what it said was illicit trading in missile technology and weapons of mass destruction.
Those companies affected by this set of sanctions will be barred from any US government contracts and US assistance, banned from buying US defence articles and denied licences to sell them for a period of two years.
Also on Tuesday, the UN atomic agency said that member states had given it fresh information alleging that Iran has worked secretly on developing nuclear arms.
The report, drawn up ahead of next month's meeting of the IAEA board, said Iran's stockpile of low-enriched uranium had continued to grow, Reuters reports.