A single article of impeachment charging Mr Trump with inciting insurrection over the January 6 violence in which five people died was laid before Congress last night.
But Mr Biden told CNN that he did not believe his Democrat colleagues could secure the 17 Republican votes needed to secure the two-thirds Senate majority needed for conviction at trial.
“The Senate has changed since I was there, but it hasn’t changed that much,” Mr Biden said.
He said that despite this, and the disruptive effect that impeachment could have on his legislative plans and efforts to unify his country, he backed the attempt to convict Mr Trump.
“I think it has to happen,” he said, warning that there would be “a worse effect if it didn’t happen”.
Mr Biden, interviewed in the West Wing, said he believed the outcome would be different if Mr Trump had six months left in his term.
The impeachment trial is the second that Mr Trump has faced. The charge cites his repeated claim that the election included “widespread fraud” and that “we won”, as well as his call at a January 4 rally for his supporters to “fight like hell”.