Vienna: Diplomats say that a July 20 target date for an Iran nuclear deal is in jeopardy because Tehran is not providing answers sought by UN experts investigating whether Tehran worked on atomic arms.

The UN atomic agency suspects Iran may have tested detonators as part of secret work on nuclear weapons. But three diplomats told The Associated Press Monday that Iran insists they were used only for conventional military or civilian blasts.

The UN agency’s probe is separate from nuclear talks between Iran and six powers, which both sides hope to finish by July 20. But the US insists that Tehran dispel agency suspicions as part of any overall deal.

Meanwhile, the UN nuclear watchdog and Iran ended a meeting on Monday without giving statements on the outcome, leaving unclear whether progress was made in efforts to help allay international concern over Tehran’s nuclear programme.

Under a transparency and cooperation pact agreed between Iran and the International Atomic Energy Agency in November, Iran was to take seven practical measures by May 15 in a phased process, including more IAEA access to nuclear-related sites.

Diplomatic sources told Reuters on Friday that the IAEA was seeking further clarification from Iran about one of those steps, concerning information about fast-acting detonators that can have both military and civilian applications.

Iran says it has already implemented the seven steps - including access to two uranium sites - but the sources suggested the IAEA still wanted more information about the so-called Explosive Bridge Wire (EBW) detonators.

Monday’s meeting took place a day before the Islamic Republic and six world powers on Tuesday resume, also in the Austrian capital, negotiations on a broad diplomatic settlement of the decade-old nuclear dispute.