"The letter was received last night and is currently being reviewed," ministry spokesman Esmaeil Baqaei told the official IRNA news agency, adding: "A decision on how to respond will be made after a thorough assessment."

The letter -- which Trump said was addressed to Iran's supreme leader Ayatollah Ali Khamenei -- was delivered to Tehran by senior United Arab Emirates diplomat Anwar Gargash.

It was not immediately clear if Khamenei, who has the final say in matters of state, had personally received the letter.

On Wednesday, Khamenei said the US invitation to talks was aimed at "deceiving" world public opinion by portraying the United States as ready to negotiate and Iran as unwilling.

He said the proposed negotiations "will not lift sanctions" but will instead "make the sanctions knot tighter".

He described the US threat of possible military action as "unwise", saying that Iran "was not seeking war, but if someone takes action, our response will be decisive and certain".

Trump, who returned to the White House for a second term in January, has reinstated his "maximum pressure" policy of sanctions against Iran, mirroring his approach during his first term.

Then Trump unilaterally withdrew from the landmark 2015 nuclear deal between Iran and world powers, and reimposed sweeping economic sanctions.

Tehran adhered to the 2015 deal for a year after Washington's withdrawal, but then began rolling back its own commitments.

There were brief efforts to revive the deal under the Joe Biden administration but they went nowhere.

Trump has called for new negotiations with Iran but Tehran has ruled out direct talks while US sanctions remain in place.

"Ultimately, the United States should lift the sanctions," Foreign Minister Abbas Araghchi said in an interview published Thursday by the government's official newspaper Iran.

"We will enter into direct negotiations when we are on an equal footing, free from pressure and threats, and are confident that the national interests of the people will be guaranteed."