Outspoken Donald Trump critic Robert De Niro has reignited his feud with the US President, saying he's "a New Yorker who I never would want to meet".

In June, the Oscar-winning actor shouted "f*** Trump" at the Tony Awards, leading to the president calling De Niro "a very Low IQ individual".

The legendary star of films such as The Godfather Part II, Goodfellas and Casino appeared on CNN on Monday where he was asked why he was so vocal about the president.

He replied: "I know what kind of person this guy is, he is a New Yorker who I never would want to meet, and now he's president. And the reason I wouldn't want to meet him is because of the kind of person he is.

"As we all know now, there's nothing new. It's disgraceful but we'll get past it. It will be like a nightmare that you remember. I will be with my trainer five years from now saying, remember all that stuff, how terrible it was.

"And at least I lived to see the time when this will all pass, like any nightmare."

De Niro has appeared on Saturday Night Live as special counsel Robert Mueller who is in charge of the investigation into Russia's alleged interference in the 2016 presidential campaign. 

When the interviewer mentioned this and said we lived in "a crazy world", De Niro responded: "I never thought in my lifetime, and I have seen a lot in my lifetime, I never thought - I was working out with my trainer the other day, we have seen horrible things over the years, but this is one of the worst I have ever seen and ever thought I would see, but it's real."

The actor was also asked if he thought he was playing into Trump's hands by responding to him.

He said: "No, because even his responses, his retorts if you will, are inane. And they are kind of stupid. He does not say anything that's even witty or smart, so it doesn't bother me. It's ridiculous."

In October, De Niro was one of the high-profile opponents of the president who had suspicious packages addressed to them.