Iranian Foreign Minister Mohammad Javad Zarif has said talks with world powers on implementing an accord on the country's nuclear programme are making 'slow progress'.
The comments from Zarif came while speaking alongside his Italian counterpart Emma Bonino, who has been visiting Tehran.
She told the BBC ties were 'improving' but the path ahead was 'difficult'.
Last month, Iran and six world powers agreed a deal to freeze Iran's nuclear programme in return for easing sanctions.
According to the BBC, Iranian negotiators had been meeting with representatives of the 'P5+1' group -the US, the UK, France, China, Russia and Germany- to discuss technical details of the deal would be implemented.
A first round of talks on how to implement the accord was suspended earlier this month when the United States expanded a sanctions blacklist, the report said.
However, as part of the deal, inspectors from the UN's nuclear agency visited Iran's Arak heavy water production plant on 8 December for the first time in more than two years, it added.
