European leaders are exploring further sanctions on Iran over its ballistic missile programme and regional meddling, as well as more extensive inspection of its atomic sites as they try to dissuade the US from abandoning a nuclear deal between world powers and Tehran. Emmanuel Macron, French president, and Angela Merkel, Germany’s chancellor, are expected to use separate official visits to Washington this week to urge President Donald Trump to stick with an accord he has threatened to withdraw from on May 12.

“This will be a chance to persuade Trump before May 12,” said one EU diplomat, hailing the “nice” coincidence of the sequential trips by the bloc’s two most influential leaders. “Iran will be a big point on the agenda.” Concern is mounting in European capitals about the fate of the deal, but they have limited room for maneuver to meet Mr Trump’s demands while keeping Tehran on board. France, Germany and the UK — the three European signatories to the 2015 nuclear accord, known as the JCPOA — are finalising their response to demands issued by Mr. Trump in January.

They are looking into ways to toughen inspections of Iranian nuclear sites, such as military installations, universities and laboratories, as well as possible new sanctions because of Iran’s ballistic missile programme and its involvement in regional conflicts such as Syria and Yemen, diplomats say.