The head of Iran’s atomic program said Friday that a third meeting would be held with the United Nations nuclear watchdog to discuss long-standing issues.

Tehran is due by June 21 to answer concerns raised by the International Atomic Energy Agency (IAEA) over work Iran carried out before 2003 in sites where the IAEA later detected traces of uranium. Some analysts have linked the traces to equipment supplied by Pakistani nuclear scientist AQ Khan.

“We have answered all the questions about the alleged locations,” Mohammad Eslami, head of the Iran’s Atomic Energy Organization said. “Negotiations are in progress.” Two meetings had been held, he added, since Iran and the agency in early March agreed the June 21 deadline.

IAEA chief Rafael Mariano Grossi in an interview with Associated Press Wednesday stressed that agency access to Iran’s nuclear program would be enhanced by the revival of the 2015 Iran nuclear deal, the JCPOA (Joint Comprehensive Plan of Action).

Year-long talks in Vienna, between Iran and six world powers, to revive the JCPOA have stalled since March. Grossi told AP that “political circumstance” needed to be overcome if the JCPOA were to be back in place and the previous level of IAEA monitoring restored.

Iran cutback the agency’s access in 2021 following the killing, widely attributed to Israel, of scientist Mohsen Fakhrizadeh, but had since 2019 been expanding its atomic program beyond JCPOA limits in response to the United States in 2018 leaving the JCPOA and imposing draconian sanctions.