Vienna - Iran continues to hamper attempts by the UN nuclear watchdog to investigate allegations it has been pursuing studies geared to nuclear weapons applications, diplomats said on Wednesday.

Inspectors from the International Atomic Energy Agency (IAEA) met with resistance from Iran when trying to discuss intelligence provided by other member states regarding so-called weaponization studies, they said.

Iran refused to discuss the matter in any depth, despite several trips to Iran by IAEA chief inspector Olli Heinonen, the diplomats said.

"It's business as usual in Tehran. Iran says the information is fabricated, and weapons applications are for conventional arms," a European diplomat said.

The IAEA in February presented its member states with intelligence regarding the design of a missile re-entry vehicle, uranium conversion experiments and high explosives testing, all with possible weapons applications.

As early as Friday, The IAEA will present a report on its progress into the six-year investigation of Iran's nuclear programme to its 35 board member states ahead of its upcoming meeting from June 2-6.

"Mr Heinonen made clear that continuing Iranian claims of 'baseless allegations' would not be acceptable. The board's expectations are equally clear; Iran's leaders must fully disclose their past activities and allow IAEA inspections to verify they are stopped," US Ambassador Gregory Schulte said.

IAEA Director General Mohamed ElBaradei has in the past expressed optimism that the IAEA would be in a position to conclude its probe by May and reiterated that the agency had found no evidence of nuclear weapons in Iran.

The report will also confirm that Tehran has ignored UN Security Council demands to stop its uranium enrichment drive, subject of three sanctions resolutions by the UN body.

Enriched uranium is a precursor for nuclear fuel, but can also be used, if enriched to a higher degree, for nuclear weapons.

The report is also expected to detail Iran's enrichment progress, which may be less advanced than claimed by Iran's President Mahmoud Ahmadinejad, who said last month Iran was more than tripling the number of its enrichment centrifuges by installing 6,000 new machines.

Iran was also experimenting with a new, more efficient centrifuge type, Ahmadinejad said. Iran says its nuclear programme is solely geared towards energy production. (dpa)