Reuters - President Donald Trump warned on Wednesday that U.S. sanctions on Iran would be increased “substantially” soon, as the U.N. nuclear watchdog held an emergency meeting at Washington’s request to weigh Tehran’s breach of a nuclear deal.

Trump also accused Iran of secretly enriching uranium for a long time but offered no evidence, and Iran said after the 35-nation meeting in Vienna that it had “nothing to hide”. U.N. inspectors have uncovered no covert enrichment by Iran since long before its 2015 nuclear agreement deal with world powers.

Washington used the session of the International Atomic Energy Agency’s Board of Governors to accuse Iran of extortion after it inched past the deal’s limit on enrichment levels over the past week, while still offering to hold talks with Tehran.

Iran says it is reacting to harsh U.S. economic sanctions imposed on Tehran since Trump pulled Washington out of the nuclear deal in 2018 and says all its steps were reversible if Washington returned to the agreement.

“Iran has long been secretly ‘enriching,’ in total violation of the terrible 150 Billion Dollar deal made by John Kerry and the Obama Administration,” Trump said on Twitter.

“Remember, that deal was to expire in a short number of years. Sanctions will soon be increased, substantially!”

While Iran was found to have had covert enrichment sites long before the nuclear accord, the 2015 deal imposed the most intrusive nuclear supervision on Iran of any country, and there has been no serious suggestion Iran is secretly enriching now in a way that would hint at an effort to develop a nuclear weapon.

The deal confines enrichment in Iran to its Natanz site, which was itself exposed in 2003. Any clandestine enrichment elsewhere would be a grave breach of the deal. It was not immediately clear from Trump’s comments whether he was referring to previous, long-known activities or making a new allegation.