Robert De Niro has attacked President Donald Trump again accusing him of having ''sullied'' the US Presidency.

The 'Goodfellas' actor has been an outspoken critic of the former 'Apprentice' host since before he moved into the White House in January to run America as the new leader.

And De Niro has not impressed by Trump's first few months in office and is beyond dismayed that he has cut funding for the arts.

In an interview broadcast on 'Good Day New York', he fumed: ''I can't articulate it well enough other than to say it's ridiculous. It's idiotic. This is guy has sullied the presidency. He's debased the presidency. It's just beyond surreal what this guy has done.''

The 73-year-old Hollywood icon previously described Trump, 70, as a ''mutt'' who he wanted to punch in the face back in October as the Republican's election campaign against Democrat candidate Hilary Clinton was at its peak and De Niro still stands by his description of the new president.

Asked if he still agrees with his previous comment, the 'Raging Bull' star replied: ''He's a mutt. Every word I said then I mean today. He has not changed.''

De Niro - who is married to Grace Hightower - wrote a letter to Meryl Streep in support of her speech at the Golden Globes in which she tore into Trump for his behaviour during his election campaign which ''stunned'' her.

His letter to 67-year-old Streep read: ''What you said was great. It needed to be said, and you said it beautifully. I have so much respect for you that you did it while the world was celebrating your achievements. I share your sentiments about punks and bullies. Enough is enough.''