President Joe Biden's son Hunter Biden defied an order by House Republicans to testify behind closed doors about his business dealings, ratcheting up tensions with lawmakers who plan to vote on Wednesday (December 13) to formalize their impeachment probe of his father.

At a news conference outside the Capitol, Biden blasted the probe as baseless and indicated he would not cooperate with a subpoena by the House Oversight Committee to testify in private.

Republican Representative Darrell Issa said he expects the panel will hold Hunter Biden in contempt of Congress if he does not show. Republicans in the House of Representatives are pushing ahead with a plan to vote on Wednesday to authorize the probe before leaving for a three-week holiday break on Thursday.

Fifty-three-year-old Hunter Biden said that "there is no evidence to support the allegations that my father was financially involved in my business, because it did not happen." The White House has denied wrongdoing and dismissed the probe as politically motivated ahead of the 2024 presidential election.