Iran and six world powers reached a breakthrough deal on Sunday to curb Tehran's nuclear programme in exchange for limited sanctions relief, in what could be the first sign of an emerging rapprochement between the Islamic state and the West.

Aimed at ending a dangerous standoff, the agreement between Iran and the United States, France, Germany, Britain, China and Russia was nailed down after more than four days of negotiations in the Swiss city of Geneva.

The accord was designed as a package of confidence-building steps to ease decades of tensions and confrontation and banish the spectre of a Middle East war over Tehran's nuclear aspirations.