FILE PHOTO: Iran's Foreign Minister Mohammad Javad Zarif smiles during a meeting with Swiss Foreign Minister Ignazio Cassis, in Bern, Switzerland, July 2, 2018. REUTERS/Denis Balibouse/File Photo

LONDON (Reuters) - Iran hit back at a U.S. offer of negotiations on Thursday, saying Washington had violated the terms of the last big deal they agreed, the 2015 nuclear accord.

U.S. President Donald Trump pulled out of that nuclear accord - which curbed Iran’s atomic activities in return for sanctions relief - in May, saying it did not go far enough.

The U.S. special envoy for Iran, Brian Hook, said on Wednesday that Washington now wanted to negotiate a treaty that included Tehran’s ballistic missile programme and its regional behaviour.

Hook said the new deal that Washington hoped to sign with Iran, would not be a “personal agreement between two governments like the last one, we seek a treaty.”

Iranian Foreign Minister Mohammad Javad Zarif took to Twitter to dismiss the characterisation of last deal as a “personal agreement”, saying it was “an int’l accord enshrined in a UN (Security Council resolution)”.

“U.S. has violated its treaty obligations too... Apparently, U.S. only mocks calls for peace,” he added in the message that was attached to a video of a protester who took to the stage after Hook’s speech, shouting that sanctions were hurting Iranian people.

The five other world powers that signed the 2015 accord with Iran - France, Germany, Britain, China and Russia - have been trying to salvage it, saying it offers the best chance to stop Iran developing a nuclear bomb. Tehran says its nuclear work is for electricity generation and other peaceful purposes.