Iran and world powers have agreed a timetable and framework agreement for working out a lasting nuclear accord, and will meet again on March 17, EU foreign policy chief Catherine Ashton said Thursday.

"We had three very productive days during which we have identified all the issues we need to address to reach a comprehensive and final agreement," Ashton said after talks in the Austrian capital.

"There is a lot to do, it won't be easy but we have made a good start," Ashton told reporters.

"We have set a timetable of meetings, initially over the next four months with a framework to continue our deliberations," she said.

"Technical experts will meet in early March and we will reconvene for the next E3+3 political directors' meeting led by ... (Iranian Foreign Minister Mohammad Javad) Zarif and myself on the 17th of March" in Vienna.

The discussions between Iran and the United States, China, Russia, Britain, France and Germany aim to transform a landmark but only interim deal that they agreed in Geneva in November into a long-term agreement.

Under the November deal, which came into force on January 20, Iran froze certain nuclear activities for six months in exchange for minor relief from sanctions and a promise of no new sanctions.