The European Union says six world powers have given Iran more details of their proposals to end a standoff over Tehran's nuclear program.
The proposals were outlined in talks in Istanbul on March 18.
In a short statement on the expert-level talks, the EU offered no indication about how the proposals were received by the Iranian experts.
At a political-level meeting in Kazakhstan last month, the two sides had agreed to hold technical discussions.
The statement by EU foreign policy chief Catherine Ashton reaffirmed that the March 18 meeting would be followed by another political-level round of talks in the Kazakh city of Almaty on April 5-6.
During the previous round in Almaty, the six powers said they were ready to offer limited sanctions relief in return for Tehran renouncing its most sensitive nuclear work.
Based on reporting by Reuters and AP