The United States said Wednesday it hoped the UN atomic agency would "very soon" give more detail on new information the watchdog has on possible military dimensions to Iran's nuclear programme.

"The real fear is that Iran is continuing ... and has over many years continued to explore and to develop technologies with no applications other than in the military sphere," Glyn Davies, US envoy to the International Atomic Energy Agency (IAEA), told reporters.

A report presented to the 35-member IAEA board in Vienna Wednesday said the agency was "increasingly concerned" about a possible military dimension to Iran's nuclear work, about which it "continues to receive new information".

"The information ... is extensive and comprehensive and has been acquired both from many member states and through its own efforts," the report presented during the multi-day regular meeting said.

"It is also broadly consistent and credible in terms of technical detail, the time frame in which the activities were conducted and the people and organizations involved."

But Iran's envoy to the IAEA, Ali Asghar Soltanieh, said that there was "no smoking gun" in his country.

"After over eight years, more than 5,000 man-days of inspections, which is unprecedented in the history of the IAEA, the IAEA has found no evidence of diversion of nuclear material to military purposes," he said.

The United Nations Security Council has imposed four rounds of sanctions on Iran, most recently in June 2010, over Tehran's refusal to stop sensitive nuclear work, most notably the enrichment of uranium.

Many Western nations suspect that Iran's programme, which Tehran says is purely peaceful, is aimed at developing nuclear weapons.

Iranian President Mahmoud Ahmadinejad said on Tuesday that his country had "no need" for nuclear weapons, telling NBC that atomic bombs were "against our beliefs and our ideology".

Soltanieh also said that Iran had shown "100 percent transparency" to Herman Nackaerts, head of the IAEA's safeguards division, in a visit to the country's nuclear facilities in August.

"I was accompanying him and I told him, 'You can go anywhere you like,'" Soltanieh said. "And he visited everywhere he wanted."

The IAEA said in its report that Iran had indeed shown "greater transparency" but that Iran was still not doing enough for the agency to verify Tehran's claims that its programme was peaceful.

Davies said meanwhile that a letter sent by Iran to EU foreign policy chief Catherine Ashton -- confirmed to AFP in Brussels by her spokesman Michael Mann -- contained nothing to calm fears about Iran's activities.

"My own view, from the narrow standpoint of the work we do here at the IAEA, [is that] I don't see ... anything new by way of an Iranian commitment to fully address the concerns that the international community has," he said.

Soltanieh said that the letter to Ashton from Iran's chief nuclear negotiator Saeed Jalili was "positive and constructive".