Washington - All four White House officials who were scheduled to testify to lawmakers on Monday in the House’s ongoing impeachment hearings have refused to testify.

The officials refusing to testify are John Eisenberg, deputy counsel to the president for national security affairs and legal adviser to the National Security Council; Robert Blair, assistant to the president and senior adviser to the acting chief of staff; Michael Ellis, senior associate counsel to the president and deputy legal adviser to the National Security Council; and Brian McCormack, associate director for natural resources, energy and science at the Office of Management and Budget.

The impeachment inquiry is investigating whether President Donald Trump withheld military funding to Ukraine in order to pressure the Ukrainian president to investigate Trump’s political rival Joe Biden and his son Hunter.  

The lawyer for the whistleblower who went public about Trump’s July 25 phone call with the Ukrainian president says he will answer written questions from Republicans, who are demanding the whistleblower testify in person.

Trump has previously compared the whistleblower to a treasonous spy who deserved the death penalty, raising concerns about the officials’ safety.