A Downing Street spokeswoman said: "The prime minister was pleased to host President Trump's special envoy to the United Kingdom, Mark Burnett, at Downing Street last night, during which he took a call from President Trump and discussed his forthcoming visit to the US.".
The call between the president and prime minister is understood to have happened on Thursday during Sir Keir's meeting with Mark Burnett, Washington's special envoy to the UK.
An Instagram story for the US Embassy in London said that, during the dinner, President Trump called Mr Burnett, who "passed the phone to the PM".
Donald Trump has confirmed he will meet Sir Keir Starmer "very soon" after the prime minister "asked to come" to the US.
She added: "Mr Burnett and the prime minister agreed on the unique and special nature of the UK-US relationship, the strength of our alliance, and the warmth of the connection between the two countries.
