"I think it was a terrible thing to say. I think it's so disrespectful to the people," Trump said in a phone interview on Fox News's "Hannity."
"And he should have said something and say, 'look, to the best of my knowledge, this is probably what I'd do.' I think what he said was so disrespectful to the process and to the people. What he said then was just disgraceful."
Biden told reporters in Arizona earlier in the day that he wouldn't say whether he supports Democrat proposals to pack the nation's highest court until after Nov. 3.
“You’ll know my opinion on court-packing when the election is over,” Biden said. “It’s a great question, and I don’t blame you for asking. But you know, the moment I answer that question, the headline in every one of your papers will be on the answer to that question.”
Trump said Biden's repeated refusal to say whether he agrees or disagrees with court packing means he supports it.
"What that means, though, really, is that they're going to do it, okay, because, obviously, that means, 100 percent, that's what they're going to do," he said.
Biden has at least four times declined to answer direct questions about court packing, while his running mate, Sen. Kamala Harris (D-Calif.) has dodged the question at least twice.
“We are on the verge of a crisis of confidence in the Supreme Court,” said Harris, at the time a Democratic presidential candidate. “We have to take this challenge head-on, and everything is on the table to do that.”
Biden, before securing the nomination, said two separate times he wouldn't support packing the court.