The head of the UN's nuclear surveillance agency pressed Iran over inspections during a visit to Tehran on Monday that was being closely watched ahead of wider nuclear talks between Iran and world powers later this week.

International Atomic Energy Agency chief Yukiya Amano said as he left on the trip he was to have "direct talks with high officials of Iran" to build on "good progress" made last week between IAEA and Iranian officials in Vienna.

He held his first meeting with Fereydoon Abbasi Davani, the official in charge of Iran's nuclear energy programme, the ISNA news agency reported.

Later Monday, Amano was to see Iran's top nuclear negotiator Saeed Jalili and Foreign Minister Ali Akbar Salehi.

The outcome of the visit was seen as an indicator of Iran's willingness to allay international suspicions of nuclear weapons research to be raised on Wednesday in Baghdad talks between representatives from Iran and from the five permanent UN Security Council members plus Germany, known as the P5+1.

Those talks will substantively delve into the issues of Iran's nuclear activities and related sanctions imposed by the West and the UN, following an ice-breaking session in Istanbul last month that ended a 15-month hiatus.

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 that "nothing is certain."

While he was conducting the trip in a "positive" mindset, he underlined: "This visit is very short, and I'm not an inspector."

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

Western countries 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 obligated to permit IAEA inspections, although it last did so in 2005.

Further, it says, if it did allow inspections there, 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."

He called the UN diplomat's presence in Tehran "a good omen".

Insisting its nuclear programme is purely civilian, Iran says it already fully cooperates with the agency and 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 is portraying itself as acting with the IAEA and engaging with the P5+1 in good faith.

It wants to see sanctions hitting its vital oil and financial sectors imposed by the West 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 within days of each other.

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 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".