Iran has proposed a new round of talks about its controversial nuclear program with the six world powers. Sa-eed Ja-lili, the country's top nuclear negotiator, said he has formally called on the six powers - the US, Russia, China, Britain, France and Germany - to return to the negotiating table.

The invitation comes in the wake of new sanctions recently imposed by the West over Tehran's uranium enrichment program, which is a potential way of making nuclear arms.

The last round of negotiations between Iran and the five permanent members of the UN Security Council plus Germany in January, ended in failure. The US and some of its allies accuse Iran of using its civilian nuclear program as a cover to develop atomic weapons, which Iran denies.