The UN nuclear watchdog chief, Yukiya Amano, arrived in Tehran Monday to demand more cooperation from Iran on its nuclear activities, as Tehran prepares to engage with world powers in crucial talks in Baghdad over its controversial nuclear programme.

The visit is Amano's first to Iran since taking up the top post at the International Atomic Energy Agency (IAEA).

Amano said Sunday that he was adopting a "constructive spirit" and positive attitude as he headed to Tehran.

"Nothing is certain but I stay positive and I go there with constructive spirit," said Amano at Vienna airport before boarding his flight for Iran.

"There has been good progress during the recent rounds of discussions between Iran and IAEA. So I thought that now is the right time ... to visit Iran and have direct talks with high officials of Iran," he added.

But he added: "This visit is very short, and I'm not an inspector".

The IAEA chief, accompanied by his chief inspector Herman Nackaerts and number two Rafael Mariano Grossi, was expected to meet Iran's atomic chief Fereydoon Abbasi Davani, top nuclear negotiator Saeed Jalili and Foreign Minister Ali Akbar Salehi.

Iran hopes the visit will lead to an accord on how to resolve disputes over the IAEA monitoring nuclear activities and draw up "a new modality to answer (IAEA) questions and clear up ambiguities", Salehi said.

Salehi was quoted Sunday as welcoming the visit as a "good omen", saying it presented an opportunity for Iran to reset relations with the IAEA, which are regularly marked by controversy over Tehran's alleged lack of cooperation.

Insisting its programme is purely civilian, Iran says it fully cooperates with the agency and has accused the Vienna-based IAEA of being manipulated by Western intelligence services.

Amano has been accused by Iran of being "biased" and "unprofessional".

The IAEA, which monitors most of Iran's nuclear activities, has fueled for several years Western suspicions over a possible military dimension to Iran's atomic programme, a doubt magnified by Iran's turbulent ties with the agency.

Amano's one-day visit follows two days of "positive" talks between Iran and the IAEA last week in Vienna, reopening dialogue after two fruitless visits by IAEA experts to Tehran in January and February.

The visit also comes just two days ahead of talks in Baghdad between world powers and Iran over the latter's nuclear ambitions, which marks the second round of talks revived in April in Istanbul after a 15-month impasse.

A reconciliation between Iran and the IAEA on new rules of cooperation and more transparency on Iranian nuclear activities could send a positive signal to the Baghdad meeting.

The five permanent UN Security Council members plus Germany, or the so-called P5+1, have demanded from Iran concrete gestures to show its willingness to reach a negotiated solution to the nuclear issue.

Iran's nuclear programme has been condemned by six UN Security Council resolutions, including four with sanctions unilaterally later strengthened by the West.

The Islamic republic's arch-foes, Israel and the United States have threatened to use a military option against Iranian nuclear installations if diplomacy fails.

The leaders of eight leading industrialised countries, the G8, called on Iran Saturday to engage in "detailed discussions" in Baghdad that could "lead towards a comprehensive negotiated solution which restores international confidence that Iran's nuclear programme is exclusively peaceful".