The U.S. House of Representatives voted on Wednesday to formally authorize its ongoing impeachment inquiry into President Joe Biden, as Republicans unite behind the effort even though they have yet to find evidence of wrongdoing by the Democrat.

The Republican-controlled chamber voted 221-212 along party lines to approve the probe, which is examining whether Biden improperly benefited from his 53-year-old son Hunter Biden's foreign business dealings, hours after the younger Biden refused a call to testify behind closed doors.

The White House has dismissed the inquiry as unsubstantiated by facts and politically motivated. Biden is preparing for a possible 2024 election rematch with his Republican predecessor, Donald Trump. Trump is the first president in U.S. history to be impeached twice and is currently preparing for four upcoming criminal trials.