By Fredrik Dahl
VIENNA (Reuters) - A U.N. watchdog report this week is expected to show little progress in an investigation into suspected nuclear weapons research by Iran, diplomats said on Wednesday, a potential sticking point in six world powers' diplomacy with Tehran.
The quarterly report by the International Atomic Energy Agency (IAEA) on Iran's nuclear program, due on Thursday or Friday, is likely to say that Iran has still not provided information that it was supposed to do more than two months ago.
The confidential document will be issued to IAEA member states less than three weeks before a self-imposed Nov. 24 deadline for Iran and the global powers to end a decade-old standoff over the Islamic Republic's atomic activities.
While the six 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 research on how to make the bomb itself.
Iran rejects Western accusations that it has been seeking to develop a nuclear weapons capability as baseless.
Western officials say Iran must step up cooperation with the IAEA to help clarify its long-standing concerns as part of a diplomatic settlement, suggesting that some of the relief from sanctions the oil-producing country wants will depend on this.
The gradual process of phasing out such punitive measures would maintain pressure on Tehran also after any deal is struck.
"Undoubtedly there will be a linkage between shedding light on Iran's past nuclear activities and sanctions relief in the future," said Ali Vaez, an Iran expert at the International Crisis Group think-tank.
Iran has promised since Hassan Rouhani, seen as a pragmatist, become president last year to work with the IAEA. But it failed to address two specific areas of the U.N. agency's inquiry by Aug. 20, as it had agreed to do, diplomats said.
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 headway by now.
"What is needed now is concrete action on the part of Iran to resolve all the outstanding issues," IAEA Director General Yukiya Amano said in Washington last week, adding that progress in recent months had been limited.
But he also appeared to acknowledge that substantive movement may have to wait until after the conclusion of the negotiations between Iran and the United States, Russia, China, France, Germany and Britain:
"Now is not the best time to make rapid progress."
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.
Western experts say Iran would now be able to amass fissile material for one bomb in a few months, if it opted for such weapons of mass destruction. The United States says it wants this so-called "breakout time" extended to at least a year.
(Editing by Mark Heinrich)