"The party that has left the negotiating table, the party that has trampled the pact must return to a normal" behaviour, Hassan Rouhani said in a televised speech.

"If the enemy truly realises that the path it took was wrong, that will be the day to sit at the negotiation table and fix any issue," the president added.

Tensions have spiked in recent weeks between Tehran and Washington, which last year pulled out of a landmark Iran nuclear accord and imposed tough sanctions on the Islamic republic.

But Washington's top diplomat appeared to soften the US stance on Sunday, saying "we are prepared to engage in a conversation with no preconditions."

Washington is "certainly prepared to have (a) conversation when the Iranians will prove they are behaving as a normal nation," Pompeo said in Switzerland, which represents Washington's interests in Iran in the absence of bilateral relations.

Pompeo however gave no indication that lifting sanctions would be on the table.

On Saturday, Rouhani insisted that Iran would not be "bullied" into talks with the United States, saying "total respect" was needed for negotiations to take place.