The 76-year-old Glasgow comedian, who lives in Florida, said the rise of Donald Trump had concerned him.
Sir Billy has also branded Brexit a “con-job” and stated his opposition to Scottish nationalism, refusing to become involved in flag-waving.
Speaking to Radio Times magazine, the comedian, actor and artist shared his fears about trends in international politics, as well as the current US president.
Sir Billy said of Mr Trump: “His rise is part of an international thing. It’s happening everywhere. I think it’s called fascism. They can call it white nationalism if they like, or alt-right, but it’s that Hitlerian lie-telling.
“Let’s wait until his time’s up. It will happen. Let’s just hope there isn’t a world war before that.”
The Big Yin, who has been suffering from Parkinson’s disease and was also successfully treated for prostate cancer, said his illness is now manageable, and he is looked after by his wife Pamela who has become a “nurse”.
The comedian has stopped using medicinal marijuana to handle the symptoms of his condition.
He said: “It was quite pleasant, but I don’t want to do that every day.”
The Glaswegian said that reports of his serious ill health – one of them put forward by Sir Michael Parkinson – are exaggerated. He does admit his touring days are over, and that after 50 years in stand-up he will not take to the stage again.
The full interview is available in Radio Times magazine on sale today.