A new and seemingly promising U.N probe of allegations that Iran worked on atomic arms has stalled, diplomats say, leaving investigators not much further than where they started a decade ago and dampening U.S. hopes of reaching an overarching deal with Tehran by a November deadline.

Expectations were high just two weeks ago, when chief U.N. nuclear inspector Yukiya Amano emerged from talks in Tehran with Iranian President Hasan Rouhani saying Iran had given "a firm commitment" to cooperation and suggesting that years of deadlock had been broken.

But two diplomats told The Associated Press that the International Atomic Energy Agency will issue a confidential report this week saying that Iran hasn't provided information to substantially advance the probe, a finding that could affect talks between Iran and six major powers.

The diplomats spoke only on condition of anonymity because they are not authorized to discuss the confidential talks. IAEA spokeswoman Gill Tudor said Wednesday that the agency would have no comment. Iran's mission to the IAEA said Reza Najafi, the chief delegate to the agency, was in Tehran and nobody else could talk to reporters.

The IAEA inquiry is formally separate from the U.S.-led talks. But Washington says a successful IAEA investigation must be part of any final deal. That now seems unlikely by the Nov. 24 deadline -- already delayed from July 31 -- even if the two sides agree by then on the rest of a deal meant to limit Iran's nuclear capacities in exchange for sanctions relief.

A determination that the probe has stalled could embarrass Amano considering his optimistic comments after Aug. 17 talks with Rouhani. It also would strengthen those in U.S. Congress and elsewhere who are skeptical of predictions that Rouhani's assumption of the presidency last year marked a turn away from confrontation on the nuclear issue.

Iran and the IAEA agreed in February to a new start to the probe after a decade of deadlock, marked by Tehran's insistence that 1,000 pages of allegations of nuclear activity were based on falsified intelligence from the United States and arch-foe Israel.

Since then, the U.N. agency has sought information on three issues: alleged experiments with detonators that can be used to set off a nuclear explosion; separate work on high-explosive charges also used in nuclear blasts, and alleged studies on calculating nuclear explosive yields.

Iran denies wanting -- or ever working on -- nuclear arms. The diplomats said that as of Wednesday morning it had provided information only on the detonators, insisting that they were used for oil exploration. While such applications are possible, the agency says that its body of interconnected information suggests that they were being tested for nuclear weapons use.

No information has been given on the other two issues, the diplomats said, although two senior IAEA experts pressed Iranian counterparts for seven hours during a visit to Tehran this weekend.

Olli Heinonen, who headed the IAEA's Iran probe until 2010, also suggested the inquiry was at a standstill, in an email to the AP.

"The tone has changed in Iran, but there are very little movements in substance," said Heinonen, who is now with Harvard's Belfer Center think tank.

The diplomats said Iranian officials dismissed IAEA requests to interview those suspected of involvement in the alleged experiments, saying that could expose the scientists to assassination attempts by Israel.