The head of the UN atomic agency called Monday on Iran to grant access to a military base where Tehran allegedly conducted nuclear weapons research, without waiting for an elusive wider accord.

"I request Iran once again to provide access to the Parchin site without further delay, whether or not agreement has been reached on the structured approach," Yukiya Amano told an International Atomic Energy Agency board of governors meeting.

He told a later news conference that this would be a "confidence-building" measure and that the agency had been given access to Parchin in 2005, albeit "to a different building".

"At that time there was no document, so why cannot Iran do the same and give us access this time," he said.

Iran has refused to give the IAEA access to places, documents and scientists involved in what the agency suspects were efforts, mostly in the past but possibly ongoing, to develop nuclear weapons.

More than a year of meetings, the latest on February 13 in Tehran, have failed to agree on a so-called "structured approach" deal to address all the allegations, which were summarised in a major IAEA report in November 2011.

Amano said Monday that "negotiations must proceed with a sense of urgency" and that he "would like to report real progress by the next meeting of the next (IAEA) board meeting in June."

He also countered Iranian suggestions that the last round of talks had seen some narrowing of positions, saying he was "not aware of any progress."

Tehran says that the IAEA's conclusions about the "possible military dimensions" of its programme are based on flawed information from Western and Israeli spy agencies, information that it says it has not been allowed to see.

It denies working or ever having worked on nuclear weapons and says that no nuclear activities have taken place at the Parchin military base near Tehran and that therefore the IAEA has no right to conduct inspections there.

The agency also conducts regular inspections of Iran's declared nuclear sites and its quarterly reports routinely outline advances in its atomic programme in spite of UN Security Council resolutions calling for a suspension. The latest report, issued last month, was no exception.

Western powers were however expected to refrain from seeking a resolution from the 35-nation IAEA board at this week's meeting condemning Iran so as not to jeopardise parallel diplomatic efforts by six world powers.

Talks last week in Kazakhstan last week saw the P5+1 -- the United States, China, Russia, Britain, France and Germany -- sweeten an offer made to Iran last year, scaling back some of their demands and offering more relief from sanctions.

Technical experts from both sides are meant to begin thrashing out the details on March 17-18 in Istanbul before chief negotiators return to Almaty on April 5-6 and Iran has expressed considerable optimism about the process.

-- New term for Amano --

Western countries were meanwhile hoping that in the current closed-door meeting, scheduled to last four days, the IAEA board would approve Amano being given a second four-year term as director general.

The 65-year-old Japanese is the only candidate but formal board approval might be delayed until June or even September -- his current term runs to December -- if any countries have misgivings.

US diplomatic cables from 2009 published by WikiLeaks said Amano was "solidly in the US court on every key strategic decision" and "DG of all states, but in agreement with us."

This irked some countries who feared Amano was a US stooge, as did his decision to publish a November 2011 report on Iran's suspected weaponisation work, something which his predecessor Mohamed ElBaradei, who had a distinctly less cosy relationship with the US, refused to do.