Joe Biden likens Donald Trump to Hitler's propaganda minister Goebbels

US Democratic presidential candidate Joe Biden said he expects "personal attacks and lies" from Donald Trump in their first televised debate on Tuesday, comparing the Republican president to Nazi propaganda chief Joseph Goebbels.

"It is going to be difficult," the former vice president acknowledged in an interview broadcast Saturday on MSNBC.

"My guess is, it's going to be just straight attack. They're going to be mostly personal. That's the only thing he knows how to do," he said of Trump.

The debate Tuesday in Cleveland, Ohio will be the first time the 77-year-old veteran politician has faced the president he has promised to unseat. The men will meet again for two more debates before the November 3 election.

But some of his supporters fear that Biden, who is prone to blunders and slip-ups, may waver in these televised duels under the rhetorical blows of the Republican billionaire -- who is also prone to blunders and slip-ups, but who is far more aggressive.

"He doesn't know how to debate the facts. He's not that smart," Biden also claimed. "He doesn't know much about foreign policy, he doesn't know much about domestic policy. He doesn't know much about the detail."

As a result, Biden predicted, "it'll be mostly personal attacks and lies; but I think the American people are on to him."

Trump himself never ceases to mock what he says is his rival's lack of dynamism, nicknaming him "Sleepy Joe" and attacking his mental acuity.

"He's sort of like Goebbels," Biden said. "You say the lie long enough, keep repeating it, repeating it, repeating it, it becomes common knowledge."

"It's not like it's going to come as a surprise. And so I'm prepared to go out and make my case as to why I think he's failed and why I think the answers I have to proceed will help the American people and the American economy, and make us safer internationally."