Donald Trump has lavished praise on Hillary Clinton in his first television interview since the election, describing the woman he has vowed to throw into prison as "very strong and very smart" and noting her grace.

Mr Trump has spent well over a year attacking "Crooked Hillary," suggesting she was on drugs, and suggesting she be assassinated - yet in an interview on Friday, to be broadcast on Sunday, he said he was impressed by her decency.

Asked about the moment Mrs Clinton called to concede defeat, Mr Trump said: "So, Hillary called, and it was a lovely call, and it was a tough call for her, I mean, I can imagine.

"Tougher for her than it would have been for me.

"I mean, for me, it would have been very, very difficult."

Flanked by his wife Melania and four oldest children, he praised his defeated rival.