Vienna, Reuters—Talks between the UN nuclear watchdog and Iran this week appear not to have substantively advanced an investigation into suspected atomic bomb research by Tehran, potentially dimming chances for a broader deal between the Iranians and big powers.

Western officials say Iran must improve cooperation with United Nations nuclear sleuths if it wants to reach a settlement to a protracted dispute with six world powers over the country’s nuclear program and be rid of crippling financial sanctions.

The International Atomic Energy Agency (IAEA) said in a statement after the October 7–8 meeting in Tehran that discussions would continue. But it did not announce a date for the next round of talks focused on the Vienna-based IAEA’s concerns that Iran had initially been supposed to address by late August.

Diplomats in the Austrian capital said it seemed that very little, if any, progress had been achieved.

Tehran’s envoy to the Vienna-based UN agency, Reza Najafi, said the discussions had been “very constructive”, according to Iran’s ISNA news agency, which did not elaborate.

Iran denies Western allegations that it is seeking to develop the capability to produce nuclear weapons, saying its atomic activities are aimed at generating electricity only.

Early last month, the IAEA said Iran had not answered questions by the August 25 target date about alleged research activities into explosives testing and neutron calculations, which could be applicable to any attempt to make nuclear bombs.

In this week’s meetings, “the two sides held discussions in relation” to these two issues, the IAEA said, adding: “The agency and Iran will continue discussions on these measures.”

The IAEA gave no further detail. But its statement suggested strongly that the Islamic Republic had still not fully implemented the steps it had agreed to carry out, answering questions about what the United Nations agency calls the “possible military dimensions” of Tehran’s nuclear program.

The IAEA has for years been trying to get to the bottom of Western intelligence reports suggesting that Iran has worked on designing a nuclear warhead.

Iran has denounced the intelligence as fabricated, but has promised to work with the IAEA since last year when Hassan Rouhani, seen as a pragmatist, became president on a platform to overcome his country’s international isolation.

Rouhani’s election raised hopes of a solution to the nuclear stand-off with the West after years of tension that raised fears of a new Middle East war. An interim accord was reached between Iran and six major powers—the United States, France, Germany, Britain, China and Russia—in Geneva last November.

But they fell short of a self-imposed July target date for a long-term accord and now face a new deadline of November 24.

While the powers seek to limit the size of Iran’s future nuclear program, and thereby extend the time it would need for any attempt to accumulate fissile material for a weapon, the IAEA is investigating alleged research and experiments in the past that could be used to make the bomb itself.