US President Donald Trump says he would take a "tougher" attitude toward Brexit negotiations than the approach now being used by British Prime Minister Theresa May.

Britain is preparing to leave European Union in March 2019. The complex negotiations have moved slowly and May's Cabinet seems divided over how best to separate Britain from the 28-nation bloc.

In an ITV interview with Piers Morgan, to be broadcast Sunday night (28 January), Trump says "would it be the way I negotiate? No, I wouldn't negotiate it the way it's (being) negotiated... I would have had a different attitude...I would have said the European Union is not cracked up to what it's supposed to be. I would have taken a tougher stand in getting out."

There have been tensions between the two leaders. In the same interview, Trump apologises for retweeting videos by a far-right group in Britain and wishes Prince Harry and Meghan Markle well with their May wedding.