The French government has asked the country’s biggest companies not to invest in Iran, as the tension mounts over Tehran’s nuclear ambitions ahead of a meeting this week of the world’s big powers.

Bernard Kouchner, France’s foreign minister, on Sunday indicated that France’s newly elected government had joined forces with Washington to solicit a sort of unofficial boycott of Iranian projects. “We have asked a certain number of our big companies not to respond to Iranian tenders. I think this has been heard and we are not the only ones to have done so,” he said in a televised interview.