Donald Trump said retweeted explicit videos shared by the far-right group to his near-50 million Twitter followers late last year.
This sparked fury in Britain and today Mr Trump finally apologised for sharing the clips.
He told Morgan: “Here’s what’s fair, if you’re telling me they’re horrible people, horrible racist people I would certainly apologise if you would like me to do that. I know nothing about them.
“I don’t want to be involved with people, but you’re telling me about these people because I know nothing about these people.
“I know nothing about them and I know nothing about them today. Other than I read a little bit. I guess, again I’m in the United States, so I didn’t read as much about it, perhaps it was a big story in Britain, perhaps it was a bit story in the UK.
“But in the United States it wasn’t a big story. I did a retweet. When you do your own tweeting, or you do your own social media, it’s fine. When you do those retweets it can cause problems, because you never know who’s doing it to start off with.
After being asked by Morgan whether he would disassociate himself from racists, the US president said: “I don’t know who they are, I know nothing about them, so I wouldn’t be doing that. I am, as I say often, the least racist person that anybody’s going to meet.
“Certainly I wasn’t endorsing anybody. I knew nothing about them. They had I guess a couple of depictions of radical Islamic terror.
“Radical Islamic terror, whether you like talking about it or not Piers, it’s a fact. You look at what’s going on in UK and you look at what’s going on all over the world, you can try and shield it.”