A U.N. nuclear agency official probing allegations that Iran worked on atomic arms says talks in Tehran were "useful" and the sides have agreed to meet again next month.

Tero Varjoranta says there was agreement to "speed up" the process, but gave no details Tuesday. The talks were the first in months, possibly indicating movement in more than a decade of repeatedly stalled attempts by the International Atomic Energy Agency to investigate the claims.

Iran denies any work on such weapons and says the suspicions are based on phony intelligence from its foes.

The U.S. says the allegations must be cleared up as part of a nuclear deal it and five other countries are negotiating with Iran. But that is unlikely by the June target date for an agreement.