British Prime Minister Theresa May has agreed to meet US President-elect Donald Trump "at the earliest possible opportunity".

Downing Street says they talked over the phone this afternoon and plan to have 'regular dialogue'.

Mrs May and the US President-elect also discussed NATO - and agreed that other members of the defence treaty should spend more on defence.

A spokesperson for Downing Street said: "They discussed NATO, agreeing on the importance of the Alliance, the need for more NATO members to meet the target of spending 2% of GDP and the role that NATO can play in addressing diverse threats.

"They discussed how the President-elect’s transition plans were progressing and agreed that their teams should continue to build close relationships through this period, including with a meeting of their national security advisers in the United States before Christmas."

The phone call came a week after Mr Trump unexpectedly took to Twitter to declare that the UK should appoint UKIP's Nigel Farage as its US Ambassador.

Many people would like to see @Nigel_Farage represent Great Britain as their Ambassador to the United States. He would do a great job!

— Donald J. Trump (@realDonaldTrump) November 22, 2016

A Downing Street spokesperson said there was "no vacancy for an ambassador to the United States", with Nigel Kim Darroch having only taken over the job early this year.

The UK's Foreign Secretary Boris Johnson added: "We have a first rate ambassador in Washington doing a very good job."