The prime minister said he recognised US concerns the 2015 deal was “flawed”, but there had to be a way of stopping Tehran from acquiring nuclear weapons.
“If we’re going to get rid we need a replacement,” he told BBC Breakfast. “Let’s replace it with the Trump deal.”
His comments came as the UK, France and Germany triggered a dispute mechanism in the deal after violations by Iran.
Foreign Secretary Dominic Raab is to make a Commons statement later amid growing fears for the future of the 2015 Joint Comprehensive Plan of Action (JCPOA), which was abandoned by the US in 2018.
Iran has suspended all limits on its production of enriched uranium, which can be used can be used to make reactor fuel but also nuclear weapons. It has said it is responding to sanctions reinstated by the US in 2018.
In a joint statement, the three European powers said Iran was not “meeting its commitments” and it was referring the issue to the body which enforces the agreement to try and ensure Tehran complied with the terms of the existing agreement as soon as possible.
“We do this in good faith with the overarching objective of preserving the JCPOA and in the sincere hope of finding a way forward to resolve the impasse through constructive diplomatic dialogue, while preserving the agreement and remaining within its framework,” it said.
The BBC’s political editor Laura Kuenssberg says she understands the PM believes the current deal has to be made to work in a format that the US will sign up to.
In a wide-ranging interview with BBC Breakfast’s Dan Walker – his first major TV interview since the election – the PM also said he was “very, very, very confident” about the UK and EU negotiating a new trade deal by the 31 December deadline.
While, in any negotiation, a country had “to budget for a complete failure of common sense”, he believed a successful outcome was “enormously likely”.
He also said the government was continuing to look at whether Big Ben would chime at the moment that Brexit happens at 23.00 GMT on 31 January. The bell is currently being refurbished and he said it would cost about £500,000 for it to be brought back into use for one night.
“We are working up a plan so people can bung a bob for a Big Ben bong,” Mr Johnson said.
What the PM said on Iran
The JCPOA, signed in 2015, saw Iran agree to limit its sensitive nuclear activities and allow in international inspectors in return for the lifting of crippling economic sanctions.
Mr Trump has described it as the worst deal ever negotiated, but the UK and its other signatories, China, France, Russia and Germany, are still committed to it.
Speaking to the BBC, Mr Johnson suggested this would remain the case until the agreement was changed.
The deal exists but in a kind of limbo – abandoned or largely abandoned by its two most important signatories, the US and Iran.
In invoking the dispute mechanism, the Europeans are taking the first formal step towards writing its obituary. They insist that they will stand by it for as long as it exists and that they want a better deal – one that the US can support.
The European decision to invoke the dispute process may be a final bowing to the inevitable. The nuclear agreement is in a critical condition and slowly slipping away.
“My point to our American friends – somehow we have to stop Iran acquiring nuclear weapons. If we’re going to get rid we need a replacement.
“From the American perspective, it’s a flawed deal… plus it was negotiated by President Obama.
“Let’s replace it with the Trump deal. That’s what we need to see. President Trump is a great dealmaker by his own account, and by many others.
“Let’s work together to replace the JCPOA and get the Trump deal instead.”
The PM defended the UK’s response to the US killing of Iranian general Qasem Soleimani, saying there was no reasons for it be informed in advance and it had played its “traditional role” in working with Washington and Europe to de-escalate tensions.
He said he was pleased that Iran had admitted to a “terrible error” in shooting down an Ukrainian passenger jet, killing all those on board.
Iran, he said, was an “amazing country” and “should be orientated towards… our way of doing things”, but “they are captive to [the current] government.”
What PM said about domestic priorities
The PM was asked what he would do to address the record waiting times in A&E departments in December, with 400,000 people having to wait more than four hours to be treated, many of them on trolleys and in corridors.
Mr Johnson said the health service would get an extra £34bn in funding over the next four years, with 50,000 more nurses and 6,000 new GPs.
“I also want to see improvements in performance, in A&E and in waiting times, across the country. We are going to be working on this flat out.”
But he asked for patience when it came to another huge issue – finding an affordable solution to the provision of social care for the elderly.
When he first entered Downing Street in July, he suggested he had a plan to fix the problem once and for all, but the Conservative manifesto only committed to urgent cross-party talks.
He insisted new proposals would be published this year but it might take the whole Parliament – which is scheduled to last more than four years – for them to come into force because of the complexity of the issue.
“This has been shirked by governments for about 30 years. We are now going to get on and deal with this so people get the care they need in their old age but do not have to sell their home to pay for their care.
“This is potentially a massive change and we have to get it right… There are quite a lot of important moral and social issues contained in it.
“Should taxpayers being paying for people who might be able to afford it…? Should families be looking after their elderly relatives?”