British Foreign Secretary Boris Johnson has called on US President Donald Trump not to scuttle the Iran nuclear deal.

In an article in The New York Times on Sunday, Johnson, who is in Washington to persuade the Trump administration to remain in the international accord, said that "it would be a mistake to walk away.”

He argued that "only Iran would gain" if the United States withdraws from the international nuclear agreement between Iran and six world powers.

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

“It has weaknesses, certainly, but I am convinced they can be remedied,” he said, adding that Britain was working with the US, France and Germany to achieve that.

Trump has declared that he would pull the US out of the nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), which lifted nuclear-related sanctions on Tehran in exchange for curbs on its nuclear program.

Johnson’s trip comes as part of last-minute diplomatic efforts to stop Trump from re-imposing sanctions on Iran on May 12, which would effectively terminate the deal signed between Tehran and the US, the UK, France, China, Russia and Germany in 2015.

He will meet senior American officials, including Vice President Mike Pence and Trump’s new National Security Adviser John Bolton, both of whom have been critical of Iran and the agreement.

In his article, Johnson called restrictions on Iran's peaceful nuclear program “handcuffs,” and said, “I see no possible advantage in casting them aside.”

He added that the “handcuffs” should be improved, not broken.

Earlier this month, Johnson highlighted the importance of maintaining the 2015 deal “while building on it in order to take account of the legitimate concerns of the US.”

Trump gave Congress and America's European allies till May 12 to help “fix” the deal, or he would withdraw the US from it.

Russia and China, as the other signatories to the JCPOA, have warned against efforts to scrap the landmark accord and pledged to continue to honor their commitments under the deal.

The International Atomic Energy Agency has been monitoring Iran’s compliance with its commitments under the nuclear deal and has consistently verified the Islamic Republic’s compliance.

On Sunday, Iranian President Hassan Rouhani said the US will regret if it withdraws from the nuclear deal.

"If the United States opts to pull out of the JCPOA, you will soon see the historic remorse which the move will bring about for" Washington, Rouhani said.