The fate of the Iran nuclear deal remains in the balance despite efforts by the leaders of France and Germany and now Britain's Foreign Secretary, to persuade the US not to pull out at the end of the week.
Boris Johnson is the latest representative of the so-called “EU three” who helped negotiate the agreement in 2015 – to meet with the US administration.
The British Foreign Secretary has arrived in Washington to try to convince the US president to keep the US in the 2015 accord.
Boris Johnson has written an opinion article in the New York Times, in which he uses a policing analogy to describe the constraints on Iran imposed by the deal as “handcuffs” that should not be cast aside.
“I am sure of one thing: every available alternative is worse. The wisest course would be to improve the handcuffs rather than break them.”
Johnson is due to meet US Vice-President Mike Pence, National Security Adviser John Bolton and foreign policy leaders in Congress. He is also expected to make several television appearances.
On Sunday (May 6 ) French President Emmanuel Macron told German online SPIEGEL, if Trump were to simply withdraw from the deal. "That would mean opening Pandora's box, it could mean war." But, he added "I don't believe that Donald Trump wants war."
Meanwhile Iranian President Hassan Rouhani has warned that it has plans to respond to any move by the US on the agreement.
"If (America) leaves the nuclear accord, it will soon see that this will entail historic remorse for it."
Tehran insists its nuclear programme is entirely peaceful and says it considers the deal non-renegotiable.
It signed it back in 2015 agreeing to curb its nuclear programme in return for the lifting of crippling sanctions.
Trump has strongly criticised the agreement, calling it "insane".
He is unhappy that it only limits Iran's nuclear activities for a fixed period and doesn't stop the development of ballistic missiles.
Trump has vowed to pull out on May 12 unless the so-called flaws of the deal are fixed.