The new International Atomic Energy Agency team, revealed by diplomats last week, will include experts from several fields to pool the Vienna-based watchdog's limited resources more efficiently.

The short IAEA document said the task force "will perform functions related to the implementation of the Agreement between the Islamic Republic of Iran and the Agency for the Application of Safeguards in Connection with the Treaty on the Non-Proliferation of Nuclear Weapons and the relevant provisions of resolutions of the (IAEA) Board of Governors and the United Nations Security Council."

Iran says its nuclear work is for nuclear power and producing medical isotopes but Western nations, Israel and many others in the international community suspect its real aim is to develop the atomic bomb.

Because the IAEA has repeatedly said that it is "unable" to conclude that Iran's activities are peaceful, the UN Security Council has called on Iran to cease all uranium enrichment, imposing four rounds of sanctions.

Enriched uranium can be used for peaceful purposes but also, at highly concentrated purities, for nuclear weapons.

The IAEA's latest quarterly report, expected later this week, is expected to reassert this assessment, as well as to say that Iran has continued to expand its activities despite the UN resolutions, increased sanctions and threats of war.

Not only is the IAEA tasked with keeping tabs on Iran's current activities, it is also attempting to probe suspicions that until 2003, and possibly since, Iran had a structured programme of research into developing nuclear weapons.

The latest in a series of attempts to persuade Iran to give the IAEA access to documents, scientists and sites involved in this alleged drive to get the bomb failed on Friday.

So far Iran has flatly rejected the claims, set out in a major IAEA report last November, and says it will only give the agency the desired access as part of a broader agreement governing its future relations with the watchdog.

In particular the IAEA wants to be able to visit the Parchin military base near Tehran where it believes Iran conducted explosives tests for nuclear warhead designs. Western nations accuse Iran of "sanitizing" the site to remove evidence.

Ban also had a tough message for Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad on human rights, their caustic comments on Israel and Iran's involvement in the Syrian civil war, UN spokesman Martin Nesirky told UN correspondents from Tehran.

The UN leader "conveyed extremely clearly and in no uncertain terms" international expectations on the nuclear dispute and a range of other topics which have led to international efforts to isolate the Islamic state, Nesirky said.

Ban went to Tehran to attend the Non-Aligned Movement summit in the face of opposition from Israel and the United States.

He called for "concrete steps to address the concerns of the International Atomic Energy Agency and to prove to the world that its nuclear program is for peaceful purposes."

The United States and its European allies accuse Iran of seeking a nuclear bomb and stonewalling efforts by the UN atomic agency to get firm information on the research which the Tehran government has insisted is peaceful.

Talks between Iran and the United States, Russia, China, Britain, France and Germany have failed to start serious negotiations on ending the showdown.

In his separate meetings with Khamenei and Ahmadinejad, Ban "regretted that little tangible progress has been achieved so far during those intensive talks" and added "that the talks needed to be serious and substantive."

Ban also condemned what Nesirky called "recent rhetoric we have heard from all kinds of quarters" about a possible Israeli or US military strike on Iranian nuclear facilities.

But the UN leader took the Iranian leadership to task over their comments on Israel.

Khamenei this month called Israel a "cancerous tumor" while Ahmadinejad has repeatedly cast doubt on Israel's right to exist.

Ban "strongly objected to recent remarks from Iranian officials denying the Holocaust and Israel's right to exist. He said such offensive and inflammatory statements were unacceptable and should be condemned by all," Nesirky said.

The Syria conflict and human rights also took a prominent role in the talks.

The UN chief urged the president and supreme leader "to use Iran's influence to impress upon the Syrian leadership the urgent need for the violence to stop and to create the conditions for genuine dialogue."

Iran has been accused of breaching UN sanctions by providing arms to President Bashar al-Assad's forces. The Tehran government has given backing to the mediation efforts of UN-Arab League envoy Kofi Annan and his replacement Lakhdar Brahimi. But it has said that Assad cannot be forced out of power.

Ban "called on all states to stop supplying arms to all sides in Syria," his spokesman said.

The UN leader reaffirmed his comments that Iran has "an important role" to play in any solution to the Syria conflict, which activists say has left about 24,000 dead.

Human rights in Iran "remains a source of concern," Ban told the country's top leaders. "He said fundamental civil and political rights should be respected," Nesirky said, amid mounting international criticism of Iran's use of capital punishment and action against political opponents and ethnic minorities.

Nesirky said that Ban had also met Saeed Jalili, former nuclear negotiator and top aide to the supreme leader and other top officials in the parliament and government.

"These have been very serious meetings and extremely detailed meetings," the spokesman commented.