A top Iranian official said he hopes a meeting on Monday with three European foreign ministers will address disagreements in nuclear talks that have hindered progress toward a deal.
Iran's Foreign Minister Mohammad Javad Zarif is due in Luxembourg for discussions with his British, French and German counterparts on the potentially historic accord that could end a 12-year standoff over the Islamic republic's atomic programme.
"Differences on the text of the agreement have been reduced but the progress hasn't been what we expected," said Abbas Araghchi, an Iranian negotiator, who was to join Zarif, according to state television.
Araghchi, a deputy foreign minister, has been in Vienna where talks between experts from Iran and the P5+1 bloc (Britain, China, France, Russia and the United States plus Germany) have sought to narrow gaps.
"We hope that during the meeting of the ministers today there will be more discussion about differences in several key issues," Araghchi said.
The meeting is to take place on the sidelines of the monthly meeting of heads of diplomacy of European Union members.
Zarif will hold talks with Britain's Philip Hammond, Laurent Fabius of France, Germany's Frank-Walter Steinmeier, and later a joint meeting with EU foreign policy chief Federica Mogherini.
There will then be bilateral talks between Iran and the three ministers.
Iran and the P5+1 have been engaged in negotiations for 21 months.
World powers say a final agreement must guarantee the peaceful nature of Iran's nuclear programme. In exchange, international sanctions that have ravaged Iran's economy would be lifted.