The United States says it has imposed sanctions against 13 foreign companies that have sold equipment or technology to Iran that could be used for making nuclear, chemical or biological weapons.
A State Department spokesman said the sanctions mean the companies will not receive any business or assistance from the US government, and that US companies are banned from dealing with them for two years.
The companies are based in China, Macedonia, Russia, Belarus, North Korea, Taiwan and the United Arab Emirates.
The spokesman said that sanctions against a number of Russian companies and institutes had been lifted as they were no longer breaching the act.
From the newsroom of the BBC World Service