By Fredrik Dahl

VIENNA (Reuters) - Iran is failing to address suspicions it may have worked on designing an atomic bomb, according to the latest report by a U.N. watchdog, potentially complicating efforts by world powers to reach a deal with Tehran on its nuclear program.

The report by the International Atomic Energy Agency said Tehran had still not provided information it was due to produce more than two months ago to help advance a long-running IAEA inquiry into suspected nuclear weapons research.

The confidential document was issued to IAEA member states less than three weeks before the Nov. 24 deadline by which Iran and six global powers are seeking to end a decade-old standoff over the Islamic Republic's atomic activities.

"Iran has not provided any explanations that enable the agency to clarify the outstanding practical measures," it said.

The IAEA was referring to two steps that Iran had agreed to carry out by late August, by providing information concerning allegations of explosives tests and other activity that could be used to develop nuclear bombs.

Iran denies any intention of seeking atomic weapons, saying its nuclear program is aimed at generating electricity.

The U.N. agency said the two sides last met on Nov. 2 in the Iranian capital and had agreed to meet again as soon as possible, but not before Nov. 24. "There is no progress, basically," one diplomat familiar with the Iran file said.

The continuing deadlock in the IAEA's investigation suggests that any renewed headway will probably have to wait until after the negotiations between Iran and the United States, Britain, China, France, Germany and Russia are concluded.

Iran wants the talks to lead to a removal of international sanctions on its oil-dependent economy, but Western officials say it must step up cooperation with the IAEA to help clarify longstanding concerns about Tehran's nuclear ambitions.

VIENNA TALKS

While the six powers want Iran to scale back its uranium enrichment program - and thereby lengthen the timeline for any covert bid to assemble nuclear arms - the IAEA is investigating allegations of past Iranian research on designing an actual bomb.

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Even though it has long been clear that the IAEA's inquiry into the possible military dimensions of Iran's program will not be completed before the target date for a deal with the powers, Western diplomats had hoped for more progress by now.

Iran and the powers will meet in Vienna from Nov. 18 to try to seal a long-term agreement resolving a stand-off that over the last decade has raised fears of a new Middle East war.

Experts differ on the need for Iran to come clean about all its alleged bomb-related work: some say that full disclosure is necessary to make sure that any such research has since ceased, while others argue this objective can be achieved without a full "confession".

Iran's arch-enemy Israel and hawkish U.S. lawmakers may pounce on any accord if they feel it does not sufficiently resolve the issue.

"Concrete progress is needed on the central issue of whether Iran has worked on nuclear weapons and is maintaining a capability to revive such efforts," said U.S. expert David Albright and former IAEA chief inspector Olli Heinonen said in a commentary this week.

The U.S.-based Arms Control Association said it would be naive to think that Iran's leaders would admit to any bomb work.

The main goal should be for an agreement to ensure that the IAEA obtains sufficient information to determine that Iran has halted any such activity, the research and advocacy group said.

(Editing by Mark Trevelyan)