The report from the International Atomic Energy Agency also reiterated that more cooperation is needed by Iran for full clarity on its present activities. Without it, the IAEA said it cannot "conclude that all nuclear material in Iran is in peaceful activities."
After years of deadlock, Iran and the IAEA agreed in November 2013 on a new attempt to probe the accusations. The US and its allies also included the investigation into a to-do list for talks with Iran meant to curb its nuclear programs in exchange for sanctions relief.
Iran denies any work on or interest in nuclear arms. It accuses Israel, the United States and other adversaries of providing phony evidence to the agency for the probe.
The IAEA is focused on 12 alleged activities that point to Iranian attempts to make such weapons, including suspicions that Tehran worked on the development on a nuclear payload for missiles. The IAEA relaunched its probe two years ago by asking for information on less sensitive work related to nuclear arms allegedly carried out by Iran, with hopes of moving to larger issues later.
Obtained by The Associated Press, the report said that Tehran had recently shared some information sought by the agency but continues to hold back on the next stage of the IAEA probe.
A senior diplomat with knowledge of the issue said the material was related to nuclear modeling and calculations that the agency suspects could be linked to arms. The diplomat, who demanded anonymity because his information was confidential, declined to say whether the information was presented by Iran as proof that the suspicions were false or if they possibly pointed to corroboration of secret nuclear weapons work.