Johnson is presently visiting Washington, where he is expected to talk Trump into staying in the international deal which was finalised in 2015, under then US President Barack Obama.

The British lawmaker will meet US Vice President Mike Pence, National Security Adviser John Bolton and foreign policy leaders in Congress, a BBC report read.

According to the said deal, Iran agreed to limit its nuclear activities, in return for lenient sanctions.

However, Trump has called it insane and has threatened to pull back.

The other members apart from the US and Iran are the UK, Germany and France. Russia and China were also present as signatories, when it was signed three years ago.

In his piece in The New York Times, Johnson has said that if the US moves away from the pact, it will only benefit Iran, who has played down any chance of renegotiation.

Boris wrote: "Of all the options we have for ensuring that Iran never gets a nuclear weapon, this pact offers the fewest disadvantages."

"It has weaknesses, certainly, but I am convinced they can be remedied.

"Indeed at this moment Britain is working alongside the Trump administration and our French and German allies to ensure that they are," he added.

On Saturday France's President Emmanuel Macron told German newspaper Der Speigel that if Trump moves away from the accord, it could start a war.

"That would mean opening Pandora’s box, it could mean war,” he said.

However he added, “I don’t believe that Donald Trump wants war.”

Macron has also urged Trump to stay in the pact during his the former's state visit to Washington.

Earlier this month, Iran's Foreign Minister Javad Zarif said that his nation will not 'renegotiate or add on to a deal' that it has 'already implemented in good faith'.

"Let me make it absolutely clear once and for all: We will neither outsource our security nor will we renegotiate or add on to a deal we have already implemented in good faith," he said in a televised speech.

Zarif also trolled the US President.

"To put it in real-estate terms, when you buy a house and move your family in it or demolish it to build a skyscraper, you cannot come back two years later and renegotiate the price," the Iranian Foreign Minister said.

Last week, in an interview with the BBC, United Nations Secretary General Antonio Guterres urged Trump to not leave the deal.

"We should not scrap it unless we have a good alternative," he said. "We face dangerous times."