VIENNA: The United Nations nuclear watchdog and Iran failed on Friday to reach an agreement aimed at resolving deepening concern about suspected nuclear weapons research by Tehran and a senior UN official said no further talks were scheduled.

“The discussions today were intensive but important differences remain between Iran and the UN that prevented agreement,” Herman Nackaerts, the International Atomic Energy Agency's chief inspector, told journalists after about seven hours of talks with an Iranian delegation in Vienna.

“At the moment we have no plans for another meeting.”

Iran's ambassador to the IAEA, Ali Asghar Soltanieh, said that “undoubtedly some progress” was made but that differences remained.

“Because it is a very complex issue... issues related to national security of a member state are something very delicate,” he said.

“But I have to say that we are moving forward ... and we are going to continue this process so that we at the end of the day will have a framework agreed by both sides.”