Secretary of state John Kerry was on Sunday meeting with the Iranian foreign minister Javad Zarif for talks expected to focus on the prospects of reaching an agreement on reducing Tehran’s atomic activities in exchange for an end to nuclear-related sanctions.

Their meeting came on the third day of the latest round of nuclear talks between Iran and six world powers – the US, Russia, China, Britain, France and Germany.

The talks have been stalled for months, over Iran’s opposition to sharply reducing the size and output of centrifuges that can enrich uranium both to levels needed for reactor fuel or the core of nuclear warheads.

Iran says its enrichment programme is only for peaceful purposes, but Washington fears it could be used to make a bomb.