MOSCOW: Iran said on Saturday it would retaliate against new sanctions imposed by the United States after President Donald Trump set an ultimatum to fix “disastrous flaws” in a deal curbing Tehran’s nuclear programme.

Describing sanctions against Larijani as “hostile action,” Iran’s Foreign Ministry said the move “crossed all red lines of conduct in the international community and is a violation of international law and will surely be answered by a serious reaction of the Islamic Republic,” state media reported.

It did not specify what any retaliation might involve.

Iran says its nuclear programme has only peaceful aims and says it will stick to the accord as long as others respect it. But it has said it would “shred” the deal if Washington quit.

Senior US administration officials told reporters Trump would work with Europeans on a follow-on deal to enshrine triggers that the Iranian government could not exceed related to ballistic missiles.

Republican Senator Bob Corker said “significant progress” had been made on bipartisan congressional legislation to address “flaws in the agreement without violating US commitments.”

On Friday, Trump agreed to waive sanctions against Iran that were lifted as part of the international deal but said it would be the last time unless conditions were met to fix what he called “significant flaws” in the deal. Trump threatened United States will withdraw from the deal.

Zarif responded on Twitter that the deal was not renegotiable and that Trump’s stance “amounts to desperate attempts to undermine a solid multilateral agreement.”

Trump, who has sharply criticised the deal reached in Barack Obama’s presidency, had chafed at having to once again waive sanctions on a country he sees as a threat in the Middle East.

“Despite my strong inclination, I have not yet withdrawn the United States from the Iran nuclear deal,” Trump said in a statement, saying the options were to fix “the deal’s disastrous flaws, or the United States will withdraw.”

“This is a last chance,” Trump said, pushing for a separate agreement and saying the United States would not waive sanctions again to keep Iran in the pact without such an agreement.

Trump laid out conditions to keep Washington in the deal. Iran must allow “immediate inspections at all sites requested by international inspectors,” he said, and “sunset” provisions imposing limits on Iran’s nuclear programme must not expire.