Tensions between Iran and the International Atomic Energy Agency (IAEA) have repeatedly flared since a 2015 deal curbing Tehran's nuclear programme in exchange for sanction relief fell apart.

In recent years, Tehran has cut cooperation with the IAEA by ramping up its nuclear activities, deactivating surveillance devices to monitor the nuclear programme and barring UN inspectors.

A plan by Britain, France, and Germany -- with US support -- to submit a new resolution against Iran comes as concerns over the rapid expansion of its nuclear programme heightened fears that Tehran might be seeking to develop a nuclear weapon.

According to the IAEA, Tehran is the only non-nuclear weapon state to enrich uranium to 60 percent, a short step from the 90 percent level needed for atomic weapons.

Iran has always denied seeking a nuclear weapon.

Diplomats told AFP that the planned censure is driven by a need to raise diplomatic pressure on Iran to come back into compliance and address the IAEA's long-standing concerns.

- 'Too little too late' -

A similar resolution was passed by the IAEA board in June.

According to a confidential draft of the censure seen by AFP, Western powers this time ask for a "comprehensive report" to be issued by IAEA head Rafael Grossi.

The report would seek to shed more light on Iran's nuclear activities, including "a full account" of Tehran's cooperation with the IAEA on uranium traces found at undeclared sites.

The resolution -- due to be submitted on Tuesday -- follows a trip by Grossi to Tehran last week for talks with President Masoud Pezeshkian and other high-ranking officials.

During his visit, Grossi also toured the Natanz and Fordo uranium enrichment plants in central Iran.

"Grossi's visit to Tehran was... too little and too late to stave off a censure from the board," Kelsey Davenport, an expert with the Arms Control Association, told AFP.

His visit was "a missed opportunity for Pezeshkian to demonstrate that he is serious about de-escalation," she said.

"Taking tangible steps to enhance IAEA oversight of Iran's nuclear programme and address the agency's questions about past undeclared nuclear activities would have quelled speculation that Iran is engaged in illicit nuclear activities," Davenport said.

- Trump's return -

Earlier this week, Iran expressed hope that talks on its nuclear programme would be conducted "away from political pressure and considerations".

During his meeting with Grossi, Pezeshkian said that Tehran was willing to resolve "doubts and ambiguities" over its programme.

Grossi's visit was seen as one of the last chances for diplomacy before Donald Trump returns as US president in January.

During his first term between 2017 and 2021, Trump imposed a "maximum pressure" policy against Iran.

This included Washington tearing up a deal on Iran's nuclear programme that had been reached under his predecessor, Barack Obama in 2015.

The landmark deal struck with the United States, China, Russia, France, Germany and Britain provided Iran sanctions relief in exchange for curbs on its atomic programme.

Efforts to revive the deal have so far failed.