"The content of the letter is not far removed from Trump's public statements and repeats the same talking points," foreign ministry spokesman Esmaeil Baqaei told a news conference in Tehran.

"Our response will be provided through the appropriate channels once the assessment is complete," he added.

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

On the same day, Khamenei effectively ruled out holding talks with the United States.

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

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.

The US approach is aimed at preventing Iran from acquiring an atomic bomb -- something the Islamic republic denies it wants.