Rafael Grossi, the director general of the International Atomic Energy Agency (IAEA), said dialogue was "absolutely indispensable" to move forward in nuclear negotiations with Tehran.

"Without that dialogue, there's not going to be any progress," Grossi told reporters at the World Economic Forum in Davos, Switzerland.

Comments from President Donald Trump and members of the new administration show "there is a disposition" to have a "conversation and perhaps move into some form of an agreement", Grossi said.

Iranian officials also recognise that talks are needed, he noted.

Iran's nuclear programme has grown "dramatically" in terms of capabilities, facilities and inventory of nuclear material since the end of Trump's previous term in 2021, Grossi added.

During his first term, Trump pursued a policy of "maximum pressure" against Iran, withdrawing the United States from a 2015 landmark nuclear deal which imposed curbs on its nuclear programme in return for sanctions relief.

Tehran adhered to the deal until Washington's withdrawal in 2018, but then began rolling back its commitments. Efforts to revive the pact have since faltered.

The IAEA said last month that a revamp of Iran's Fordo enrichment plant would lead to an increase in the rate of production of uranium enriched up to 60 percent, closer to the 90 percent needed to make a nuclear weapon.

The rate of production will jump around sevenfold to more than 34 kilogrammes (75 pounds) of highly enriched uranium per month, it said.

"I think this is a clear indication of an acceleration. They're pressing the gas pedal," Grossi said.

Iran insists on its right to nuclear energy for peaceful purposes, and denies it is seeking an atomic weapons capability.