Former Vice President Joe Biden confirmed Friday he would not comply with a subpoena to testify in a Senate trial of President Donald Trump.

The Democratically controlled U.S. House of Representatives impeached Trump earlier this month alleging Trump abused his presidential power by tying foreign aid approved by Congress to a politically motivated investigation into a company on which Biden’s son Hunter Biden served on the board.

Leaders in the House and Republican leaders in the GOP-controlled U.S. Senate are trying to come to terms for an impeachment trial. Biden said in early December he wouldn’t comply with a subpoena by the Senate, and confirmed that statement Friday in an interview with the Des Moines Register’s editorial board. He has not been subpoenaed, but Trump's allies have floated the idea.