Iran halted its most high-level uranium enrichment in line with a deal with world powers that clears the way for an easing of sanctions.

Iranian state TV and the International Atomic Energy Agency said the authorities had halted enrichment of uranium to 20 per cent by disconnecting centrifuges in Natanz and Fordo.

International inspectors were present as Iran began implementing its obligations under the historic deal reached in Geneva on November 24.

Official news agency IRNA said that Iran had also started to convert its stockpile of 20 per cent enriched uranium to a more stable oxide of uranium.

The landmark measures are expected to lead to the lifting of some sanctions.

US officials have put the total relief figure at around $7 billion (£4.2bn) of an estimated $100bn (£61bn) in Iranian assets in foreign banks.

Iran should receive the first $550 million (£335m) instalment of $4.2bn (£2.6bn) of its blocked overseas assets on February 1.

Under the historic deal, Iran agreed to halt its 20 per cent enrichment programme but will continue enrichment up to 5 per cent.

It also agreed to convert half of its stockpile of 20 per cent enriched uranium to oxide and dilute the remaining half to 5 per cent over a period of six months.

The country's nuclear authority will also refrain from commissioning its under-construction 40-megawatt heavy water reactor in Arak.

In return, it receives a halt to new sanctions and the easing of existing sanctions.

Measures targeting petrochemical products, gold and other precious metals, the car industry, passenger plane parts and services will be lifted immediately.

The Geneva deal allows Iran to continue exporting crude oil at its current level, which is reported to be about one million barrels a day.

Iranian conservatives have called the deal a "poisoned chalice," highlighting the difficult task President Hasan Rouhani faces in selling the accord to sceptics.