The US has wasted no time in reacting to Iran’s announcement that it has started enriching its own uranium.
Washington has imposed sanctions on four subsidiaries of a construction firm run by Iran’s Islamic Revolutionary Guards.
An individual commander is also named in the action.
Sanctions had already been in place against Khatam al-Anbiya Construction, but now four of its spin-off companies are included.
The sanctions mean there is a ban on transactions between the firms and US companies.
Washington says profits from Revolutionary Guard commercial activities help support nuclear programmes.