The chief UN nuclear inspector said Wednesday that there was "still a lot of work to do" with Iran over its contested atomic programme, after returning from a three-day trip to Tehran.

"We are committed to resolving all the outstanding issues and the Iranians said they are committed too. But of course there is still a lot of work to be done, and so we have planned another trip in the very near future," Herman Nackaerts told reporters at Vienna airport.