Diplomats say that the U.N.'s International Atomic Energy Agency is set to report little progress in its attempts to probe allegations that Iran worked on nuclear arms.

Two diplomats say the agency's restricted report will likely be released to the U.N. Security Council and the IAEA's 35 board member nations Thursday. They demanded anonymity because they are not authorized to discuss the report's contents.

Iran agreed a year ago to work with the IAEA. But — like previous probes — the investigation quickly stalled over Tehran insistence that it never wanted or worked on such weapons.

The IAEA also is expected to report that Iran is honoring commitments to put temporary restraints on its atomic activities as it negotiates on a long-term nuclear deal with the U.S. and five other powers.