"There are still a lot of outstanding issues," Tero Varjoranta, deputy director general of the International Atomic Energy Agency (IAEA), said at Vienna airport after returning from the Iranian capital. "We will address them all in due course."

Iran and six powers agreed late last year on an interim deal to curb Tehran's nuclear work in exchange for some easing of sanctions. Both sides will next week start talks on a long-term agreement.

Diplomats say the way the Iran-IAEA talks progresses will be important also for the outcome of the big powers' diplomacy, which the West hopes will lead to a settlement.

"Continued progress on resolving PMD issues will go a long way to demonstrate to the international community that Iran is not pursuing nuclear weapons and is willing to come clean about its past activities," Kelsey Davenport of the Arms Control Association, a U.S. research and advocacy group, said.

The IAEA said on Sunday that Iran had agreed to take seven new practical measures within three months under a November transparency deal with the IAEA meant to help allay concern about the nuclear program.

NJF/NJF