US President Donald Trump has threatened to ratchet up sanctions on Iran following a UN emergency meeting which addressed the country’s violation of the 2015 nuclear accord.

Tehran revealed it had breached the nuclear pact for a second time due to the reimposition of punishing economic sanctions by the Trump administration which had abandoned the deal last year.

On Wednesday, Mr Trump issued an abrupt warning on Twitter saying sanctions would be increased “substantially” soon after accusing Tehran of extortion. 

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

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

Iran has long been secretly “enriching,” in total violation of the terrible 150 Billion Dollar deal made by John Kerry and the Obama Administration. Remember, that deal was to expire in a short number of years. Sanctions will soon be increased, substantially!

— Donald J. Trump (@realDonaldTrump) July 10, 2019

Iran maintained all its steps were reversible if Washington returned to the deal. 

In response to Mr Trump’s comments, Iran’s ambassador to the International Atomic Energy Agency (IAEA) Kazim Gharib Abadi told reporters it had “nothing to hide”.

It was not immediately clear from Mr Trump’s comments whether he was referring to previous, long-known activities or making a new allegation.

Last week, Iran announced that it had begun stockpiling low-enriched uranium beyond the 300-kilogram level allowed under the terms of the 2015 agreement.

The IAEA meeting in Vienna was called at the request of Washington after Iran announced that it will gradually suspend some of its obligations under the nuclear deal.

Iran’s ambassador Mr Abadi said in a German newspaper interview published earlier in the day that Tehran intended to preserve the nuclear deal if all other signatories honoured their commitments under it.

“Everything can be reversed within a single hour – if all of our partners in the treaty would just fulfil their obligations in the same way,” he told the weekly Die Zeit.

In the past two weeks Iran has breached two limits pivotal to the 2015 deal, which aimed to extended the time Iran would need to obtain enough fissile material for a nuclear weapon, if it chose to do so, to a year from around 2-3 months.

“There is no credible reason for Iran to expand its nuclear programme, and there is no way to read this as anything other than a crude and transparent attempt to extort payments from the international community,” the US mission to the IAEA said in a statement delivered at the closed-door agency board meeting.

“We call on Iran to reverse its recent nuclear steps and cease any plans for further advancements in the future.

“The United States has made clear that we are open to negotiation without preconditions, and that we are offering Iran the possibility of a full normalisation of relations.”

-with AAP