"I would honor whatever the Congress in fact legitimately asked me to do," Biden said at a campaign event in Tipton, Iowa.
His comments came one day after he said in an interview with the Des Moines Register that he would not comply with a Senate subpoena because it would be a tactic by Trump to distract from the president's wrongdoing.
Some legal experts and commentators had criticized Biden for his remarks to the Iowa newspaper, noting that the White House's refusal to comply with congressional subpoenas was part of the reason why Trump had been impeached.
Trump was impeached on Dec.
18 by the Democratic-led House of Representatives on two charges over his pressuring Ukraine to announce an investigation of Biden, a former vice president and a top contender for the Democratic presidential nomination, and Biden's son.
Trump has been charged with abuse of power and obstructing Congress' investigation.
Trump has said he did nothing wrong.