The deadline for an Iran nuclear deal has been extended to the end of June after talks in Vienna failed to reach a comprehensive agreement, diplomats say.UK Foreign Secretary Philip Hammond said good progress had been made, but it was "not possible to get an agreement by the [original] deadline".
Six world powers want Iran to curb its nuclear programme in return for the lifting of UN sanctions.
Tehran says it is not seeking nuclear weapons, but wants atomic energy.
The six countries - the US, UK, Russia, China, France and Germany - have been in negotiations with Iran to finalise a preliminary deal reached last year in Geneva.
Speaking after the Vienna talks had ended, Mr Hammond said that negotiations would resume in December, and would be extended until 30 June 2015.
Iran would be allowed to continue accessing $700m (£450m) per month in frozen assets during that period.
Russian Foreign Minister Sergey Lavrov said he expected the "basic principles" of the nuclear deal to be agreed within three to four months.