"It's a last-ditch effort in this desperate campaign to smear me and my family," Biden told Wisconsin television channel WISN.

"The vast majority of the intelligence people have come out and said there's no basis at all," he said, calling the allegations "garbage".

Pressure has been growing on the former vice president to explain his son Hunter's past foreign business dealings as well as his own involvement.

The Wall Street Journal's editorial board argued Biden owed the public an explanation rather than dismissing the claims, especially those related to financial dealings with China.

Trump on Tuesday called on Attorney General Bill Barr to launch a corruption investigation into Hunter Biden, demanding the findings be released before the November 3 election.

The president has long made unsubstantiated corruption claims about Biden, which were fuelled by reporting in the New York Post last week.

The tabloid reported on a batch of emails it obtained from a laptop supposedly left by Hunter Biden at a repair shop, suggesting that Joe Biden had used his former position as vice president to enrich his son.

Biden has consistently denied all wrongdoing, saying he did not speak to his son about his business.

Australian Associated Press