Tehran and the UN's nuclear watchdog said Wednesday that they had reached an agreement to allow the International Atomic Energy Agency the access it has requested to two sites in Iran.

"Iran is voluntarily providing the IAEA with access to the two locations specified by the IAEA," the two sides said in a joint statement, adding they had agreed on dates for the access and the verification activities there.

IAEA Director General Rafael Grossi travelled to Tehran this week in the Argentine's first visit there since taking on the top post at the agency last year.

On Tuesday, Iran's nuclear body said it held "constructive" talks with Grossi at a time of increased tensions over a US bid to reimpose UN sanctions.

In the statement issued by the IAEA, the two sides said the agreement followed "intensive bilateral consultations" and that the IAEA had no further access requests.

"Based on analysis of available information to the IAEA, the IAEA does not have further questions to Iran and further requests for access to locations," it said.

"Both sides recognise the independence, impartiality and professionalism of the IAEA continue to be essential in the fulfilment of its verification activities."

The IAEA monitors Iranian atomic activities on the ground with a 2015 landmark accord curbing Tehran's nuclear programme in exchange for sanctions relief.

The agreement has been faltering since US President Donald Trump pulled out of it in 2018 and re-imposed sanctions with remaining participants -- China, Britain, France Germany and Russia -- struggling to save it.

Access to the two disputed sites had been blocked for months, prompting a diplomatic row.

Iran had argued that the IAEA's access requests are based on allegations from the country's arch-enemy Israel and have no legal basis.

After meeting Grossi, head of Iran's atomic agency, Ali Akbar Salehi, said a "new chapter" had started.