Report on Whether Iran Was Making Nuclear Bomb Won't Be Clear Cut

A U.N. report on whether Iran has in the past carried out work related to nuclear weapons will not reach a definitive conclusion on the subject, the chief of the U.N. nuclear watchdog said on Thursday.

The report by the International Atomic Energy Agency (IAEA) is required under a landmark deal between major powers and Iran, which provides for a lifting of sanctions against the Islamic Republic in exchange for restrictions on its nuclear program.

A clear verdict that weapons-related work occurred would have made it difficult for the deal to proceed, but diplomats have said for weeks that they do not expect the report to be clear-cut, which IAEA chief Yukiya Amano confirmed on Thursday.

"The report will not be black and white," Amano told a news conference when asked about the final assessment of possible military dimensions, or PMD, file which is due next week.

In November 2011, the IAEA issued an annex to a regular report on Iran, listing twelve issues which could indicate Iran might have had a nuclear weapons program.

Iran denies these allegations, but the IAEA, which says it takes no information at face value, has described the intelligence from its member states which formed the basis of the PMD file as "overall credible".

The annex talks about specific technology to synchronise detonators, create neutron bursts to induce fissile chain reactions as needed for a nuclear bomb as well as engineering studies into missile payloads and their behaviour when launched.

The investigation leading to the report, which is aiming to answer questions on these and other points that have gone unanswered for years, had given the agency a better understanding of the "whole picture" of Iran's past nuclear activities, Amano said, but gaps remained.

"What I can now say is that this is an issue that cannot be answered by 'yes' and 'no'," Amano said.

Technically, Iran took the crucial hurdle towards sanctions relief with respect to the PMD file on Oct. 15, when it provided the agency with enough data to allow the written assessment.

Still, the report will be seized upon both by opponents and supporters of the July deal, which is designed to eventually lift sanctions.

When asked about the likely response, Amano said the PMD document would be "factual" and that any decision on further investigation was in the hands of the IAEA's member states. (Editing by Louise Ireland)