United Kingdom, Nov. 3 -- George Clooney believes that the Democrats made a "mistake" by putting Kamala Harris up against Donald Trump in the US presidential election.

The 64-year-old actor wrote a New York Times op-ed calling for incumbent Joe Biden to step aside ahead of last November's poll but feels that the party should have held a primary instead of selecting the then Vice President to "run against her own record".

Clooney told CBS Sunday Morning: "I wanted there to be, as I wrote in the op-ed, a primary (election to select a new Democratic candidate). Let's battle-test this quickly and get it up and going.

"I think the mistake with it being Kamala is she had to run against her own record. It's very hard to do if the point of run...