Theresa May has directly appealed to Donald Trump not to end the Iran nuclear deal, arguing it is "vitally important for regional security".

The Prime Minister called the US president on Tuesday evening after it was announced he will deliver his decision on his "overall Iran strategy" later this week.

US officials have said Mr Trump is expected to "decertify" the deal, having described it as an "embarrassment" and "the worst deal ever negotiated".

Britain and other European signatories to the 2015 deal, which ended sanctions on Tehran in return for Iran agreeing to give up its nuclear weapons programme, have launched urgent diplomatic efforts to save it.

Boris Johnson, the Foreign Secretary, called Rex Tillerson, his US counterpart yesterday to argue the deal was “making the world a safer place”.