Iran's Press TV confirmed that Ashton, the foreign policy chief for the European Union, and Iranian nuclear negotiator Saeed Jalili would meet May 15.
U.N. weapons inspectors this year said they weren't able to check military compounds in Iran to confirm the country's peaceful intent. Iran is suspected of pursuing the technology needed to produce a nuclear weapon, an allegation it denies.
Ashton presided over two rounds of talks in Kazakhstan between Iran, the five permanent members of the U.N. Security Council and Germany. She said negotiators in April were looking for a "balanced" position from Iran regarding what she described as a "very clear and concise proposal for confidence-building measures."
February talks in Kazakhstan included efforts to get Iran to suspend some nuclear research in exchange for an easing of economic sanctions.
A spokesman for Ashton's office told UPI via email that talks May 15 are meant as a "follow-up to the last round of negotiations held in Almaty."
Iran said recently that nuclear researchers may consider nuclear fuel enrichment levels of uranium beyond 20 percent, a level considered a breakthrough on the path toward a nuclear weapon.