Trump has signaled that he would pull the US out of the 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 reimposing 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 officials during his two-day trip, 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.
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.”
Meanwhile, Trump spoke with British Prime Minister Theresa May on Saturday on the issue, the White House said in a statement.
During his phone call with May, Trump “underscored his commitment to ensure that Iran never acquires a nuclear weapon”
Both leaders also reiterated they are looking forward to Trump's visit to the UK in July.
The US president has described the JCPOA, which was negotiated under his predecessor Barack Obama, as “the worst and most one-sided transaction Washington has ever entered into,” a characterization he often used during his presidential campaign, and threatened to tear it up.
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.
