IAEA deputy director Rafael Grossi, one of the top officials in negotiations over Iran's nuclear program, has announced his resignation, the UN nuclear watchdog said Sunday.
"I can confirm Assistant Director General Rafael Grossi has submitted his resignation from the IAEA," an International Atomic Energy Agency spokeswoman told the AFP news agency.
"The timing of his departure will be defined very soon," she added.
No reasons were given for the Argentinian's resignation, which comes as chief inspector Herman Nackaerts of Belgium prepares to retire later this year.
Nackaerts and IAEA number two Grossi led fruitless talks with Iran last year over its controversial nuclear program, which Tehran continues to insist is merely for peaceful purposes, as it affirms its intent on obliterating the Jewish state.
During a series of meetings in Vienna and Tehran, the two tried but failed to get Iran to allow IAEA inspectors greater access to its nuclear program.
Tero Varjoranto of Finland is due to take over from Nackaerts as chief inspector in October.
IAEA chief Yukiya Amano was meanwhile elected last month to a second four-year term, which will start in December, according to AFP.