Qatar's foreign minister met his Iranian counterpart Monday, after Doha signalled its intention to mediate between Tehran and Washington over a landmark nuclear deal, an AFP journalist said.

The meeting comes as the 2015 deal between Iran and world powers limiting Tehran's nuclear programme in exchange for international sanctions relief is hanging by a thread.

Doha, a close US ally, also has good relations with Tehran.

Qatar's Sheikh Mohammed bin Abdulrahman Al-Thani met in Tehran with Iranian Foreign Minister Mohammad Javad Zarif.

Iran's presidency said the minister also met with President Hassan Rouhani, to whom he delivered a message from the Emir of Qatar, Sheikh Tamim bin Hamad Al-Thani.

Former US president Donald Trump withdrew from the accord in 2018 and reimposed sanctions on Tehran, with Iran a year later gradually suspending its compliance with most key nuclear commitments in response.

The new administration of President Joe Biden has expressed willingness to return to the deal, but insisted that Iran first resume full compliance, while Tehran has called for the immediate lifting of sanctions.

Iran has said it will restrict nuclear inspections later in February if US sanctions are not lifted, or other key parties to the deal do not help Tehran bypass them, according to a law passed by the conservative-dominated parliament in December.

On Monday, Iran's ambassador to the Vienna-based International Atomic Energy Agency (IAEA), Kazem Gharibabadi, wrote on Twitter that the law "will be executed on time", giving February 23 as the date.

"The IAEA has been informed today to ensure the smooth transition to a new course in due time," he added.