Director-General Amano told the 35-nation board of the International Atomic Energy Agency meeting in Vienna that access was needed "without further delay," irrespective of whether a wider accord was finalized next month.

Iran and six world powers are due to return to Kazakhstan on April 5 for further talks, which were adjourned last week and are aimed at finding a "structured approach" to the long-standing row over Iran's nuclear program.

Iran says its research, which has included the installation of new centrifuges at its Natanz plant, is aimed primarily at producing electricity. Highly enriched uranium can also be used in a nuclear weapon.

Satellite imagery

Western diplomats quoted by the news agency Reuters said satellite imagery suggested that Iran was rebuilding a wing of Parchin where several smaller buildings were demolished last year.

Iran has denied cleansing the site of incriminating evidence.

Visiting Riyadh in Saudi Arabia, US Secretary of State John Kerry said there was "a finite amount of time" to clarify doubts about Iran's program.

At the four-day closed-door IAEA board meeting, a decision could emerge on whether Amano will get a second four-year term.

The 65-year-old from Japan is the only candidate. His current term runs to December.

ipj/mkg (Reuters, AFP, AP)