The International Atomic Energy Agency board started a meeting in Vienna on Monday. Members are expected to discuss recent developments in Iran and North Korea.
Iran has ramped up uranium enrichment since the US pulled out of the 2015 nuclear deal and re-imposed sanctions against Tehran.
Speaking to reporters on Monday, IAEA Director General Rafael Grossi expressed concerns about the tough situation his agency faces in monitoring Iran's nuclear program. He said the IAEA's inspection activities there are being hampered.
Grossi obtained permission during his recent trip to Tehran for IAEA inspectors to access surveillance cameras at Iran's nuclear facilities. But Tehran won't allow the agency to conduct unannounced inspections.
The UN nuclear watchdog also expressed grave concerns over North Korea's nuclear development activities. The agency recently said in a report that there are signs that the North resumed the operation of a nuclear reactor in Nyongbyon in early July.