Britain's foreign secretary, Boris Johnson, has scheduled talks with US officials in Washington this week. His trip follows visits in recent weeks by France's Emmanuel Macron and Angela Merkel of Germany, who also tried to convince Trump to stick with the agreement. All three European countries signed the 2015 deal, along with Russia and China.

In an article published on, Johnson wrote that the agreement offered the fewest disadvantages of all the options available. "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 wrote.

Iran's President, Hassan Rouhani, warned Trump on Sunday that leaving the nuclear deal would be a "historic regret".

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The chairman of the US House Armed Services Committee, Mac Thornberry, also advised against pulling out of the accord without a clearer idea of the consequences and urged Trump to give the Europeans time to address his concerns.

"So maybe the best thing is for the president to delay a bit more his deadline of this month and put the French and the British up to the test about whether it is possible to get this other sort of agreement," Thornberry, a Republican,  said on Fox News Sunday.

AP