IAEA chief Yukiya Amano met Iran's nuclear chief and top negotiator on Monday in a visit to Tehran closely watched for signs as to how wider talks between Iran and world powers might unfurl on Wednesday.

He sat down separately with Saeed Jalili, Iran's national security supremo tasked with negotiating nuclear issues, and atomic energy head Abbasi Davani in an effort to press for greater cooperation between Iran and the UN nuclear surveillance agency.

Amano said before arriving in Iran that he aimed to build on "good progress" made last week between lower-ranking officials from both sides at the International Atomic Energy Agency's headquarters.

Abbasi Davani's Iranian Atomic Energy Organisation issued a statement after the first meeting saying issues were raised "in a frank manner and proposals were made to remove ambiguities and to develop cooperation." It did not elaborate.

Amano made no immediate comment. After his meeting with Jalili, he was to hold discussions with Foreign Minister Ali Akbar Salehi.

The outcome of his visit was to be weighed as an indication of how willing Iran is to allay international suspicions it has conducted nuclear weapons research.

Those questions were to be raised on Wednesday in Baghdad talks between representatives of Iran and of the permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- plus Germany, the so-called P5+1.

The very fact Amano himself was in Tehran on Monday -- on his first trip to Iran since taking the helm of the IAEA -- raised speculation that the Islamic republic could grant the IAEA access to a key military installation, Parchin, outside Tehran, for the first time in seven years.

But Amano, while avoiding giving any details of what he was to discuss, stated on leaving Vienna that "nothing is certain."

He said that, while he was "positive" going into the talks, "this visit is very short, and I'm not an inspector."

Tehran this year rebuffed repeated requests from IAEA chief inspector Herman Nackaerts to send a team to verify Western intelligence suggesting Parchin could have hosted explosives testing for nuclear warheads in a special metal chamber.

Western governments have accused Iran of removing evidence at the site, while Amano has said satellite imagery showed unspecified activity.

Iran says Parchin is not a designated nuclear site and thus it is not obliged to permit IAEA inspections, although it last did so in 2005.

It says if it did allow inspections of the site, they would have to be part of an agreed "road map" that would address the IAEA's concerns in a set order.

Salehi, quoted in the Donya-e-Eqtesad newspaper ahead of Amano's visit, said: "The focus of the visit will be on the issue of modality. We hope the two sides can reach an agreement and draw up a new modality to answer (IAEA) questions and clear up ambiguities."

Insisting its nuclear programme is purely civilian, Iran has accused the Vienna-based IAEA of being manipulated by Western intelligence services.

Tehran has also repeatedly denounced what it calls the "biased" and "political" actions of Amano when dealing with Iran.

Iran wants to see Western sanctions targeting its vital oil and financial sectors eased. Its officials insist that they are having no effect, despite analysts and traders' information to the contrary.

Those sanctions are programmed to be ratcheted up further in just over a month's time, when US and EU measures aimed at blocking Iran's foreign oil sales come fully into effect.

The United Nations has also imposed its own set of non-economic sanctions on Iran in a series of resolutions that call for the Islamic republic to suspend all uranium enrichment, something Tehran has repeatedly refused to do.

On Sunday, most Iranian lawmakers issued a joint statement demanding the P5+1 members respect their nation's "rights" -- implying uranium enrichment, among other activities -- and to "change their policy of confrontation".

The spectre of military action against Iran by the United States or its ally Israel -- the sole if undeclared nuclear weapons state in the Middle East -- looms should the nuclear talks fail to make headway.

Russia, which has provided diplomatic cover to Tehran, has warned against the West launching any "hasty" strikes on Iran, saying they could trigger "a fully-fledged regional war".