Not normally known for his flattery, the US president told Theresa May in a phone conversation that she could become the next Winston Churchill, it has been reported.

After he watched the Oscar-nominated film Darkest Hour, Donald Trump is said to have made a comparison between the wartime leader, played by Gary Oldman and the current prime minister.

Three sources familiar with the phone call on 19 December last year, told the Telegraph that the US president said: "You could be this generation's Churchill".

The remarks have been confirmed by the White House and Downing Street and are said to have followed May saying that Churchill had been voted the greatest Briton ever.

A UK government source said that when the pair talk on the phone, Trump often says: "Theresa, you're doing a fantastic job, Brexit is going to be great".

It suggests that ties between the leaders on both sides of the Atlantic are warmer than believed, especially after suggestions that Trump was put out by criticism May had made about the US president's retweeting of a message by a racist far-right group.

Trump also pulled out of a visit to the UK to open the new US embassy in London, purportedly because he thought the move was not a good deal, although there were reports he feared a frosty welcome.

Trump and May will meet on Thursday on the sidelines of the World Economic Forum in Davos, to discuss cooperation over North Korea's threat, Iran's nuclear programme and the Syrian civil war.

Former UK ambassador to the US, Peter Westmacott, told Bloomberg: "The relationship has taken some knocks but there is so much substance to the relationship—commercial, defence, intelligence, foreign policy, cyber, culture, language and shared values—that we all have an interest in ensuring that it remains strong."