Its inclusion in any deal, along with Iran’s support to armed groups across the region, has also been emphasised by US officials including Rubio.
“When we were attacked by Israelis and Americans, our missiles came to our rescue so how can we accept depriving ourselves of our defensive capabilities,” Takht-Ravanchi stressed.
The senior diplomat, who is playing a key role in the current talks as he did in the negotiations more than a decade ago, also expressed concern about the American president’s conflicting messages.
“We are hearing that they are interested in negotiations,” he said. “They have said it publicly; they have said it in private conversations through Oman that they are interested to have these matters resolved peacefully.”
But in his latest remarks, Trump focused again on regime change, musing: “It seems that would be the best thing that would happen.”
“We are not hearing that in the private messages,” Takht-Ravanchi observed, referring to the notes being passed through Oman’s foreign minister Sayyid Badr bin Hamad Al-Busaidi, who is now the main Arab mediator, with other regional powers also playing a significant role, including Qatar.
Takht-Ravanchi also questioned the US military build-up in the region, warning another war would be “traumatic, bad for everybody… everybody will suffer, particularly those who have initiated this aggression”.
He added: “If we feel this is an existential threat, we will respond accordingly.” As to whether Iran would regard an American campaign as a battle for survival, he replied: “It is not wise to even think about such a very dangerous scenario because the whole region will be in a mess.”
Iran has repeatedly made it clear that US military bases in the region would be regarded as a legitimate target.
In previous attacks, including on the Al-Udeid military base in Qatar after the US struck Iranian nuclear sites last June, Tehran avoided causing American casualties.
Asked about more than 40,000 US soldiers now being posted in the region, Takht-Ravanchi replied “it would be a different game”.
Senior Iranian officials have been engaged in intensive discussions with their counterparts across the region, who have in turn been on the phone to President Trump about the urgency of avoiding a war that would have far-reaching repercussions.
“We see an almost unanimous agreement in the region against war,” Takht-Ravanchi said.
Iran has repeatedly accused Israel of trying to sabotage this negotiating track.
“We are hopeful we can do this through diplomacy, although we can’t be 100% sure,” he reflected, adding Iran has “to be alert so we are not surprised”.
That is a reference to Israel’s unexpected attack last June, which triggered what is now known as the 12-day war, just days before Iran was preparing to meet US Envoy Steve Witkoff for a sixth round of indirect talks in Oman. It has left Tehran with little trust in this process.
Iran is known to have been dismayed by the lack of progress in last year’s talks, with Witkoff understood to have often attended without experts on what is a highly technical matter.
Iranian officials, including President Masoud Pezeshkian, have been critical over understandings reached in one round often being changed by the time of the next meeting.
The presence of the US president’s son-in-law Jared Kushner at the last talks in early February has been seen by Iran as a positive signal of greater US engagement.
On the other side, questions have been raised about Iran’s readiness to make the hard compromises essential for any agreement.
Many observers remain sceptical that a new accord is within reach but Takht-Ravanchi said Iran would head to the next round in Geneva with hope that a deal could be done.
“We will do our best but the other side also has to prove that they are also sincere,” he said.
The BBC’s chief international correspondent Lyse Doucet is reporting from Tehran on condition that none of her material is used on the BBC’s Persian Service. These restrictions apply to all international media organisations operating in Iran.