House investigators hoped former national security adviser John Bolton would provide some voluntary information for their impeachment inquiry.
But Bolton's lawyer said he won't testify without a subpoena.
Chairs of the House Intelligence, Foreign Affairs and Oversight committees sent a letter to Bolton's lawyers asking for a voluntary appearance on November 7.
The move to hear from Bolton stems from the testimony of former Russia adviser Fiona Hill.
She reportedly said Bolton told her to alert the National Security Council lawyer about a “rogue operation” involving the President's personal lawyer Rudy Giuliani, White House Chief of Staff Mick Mulvaney and ambassador to the EU Gordon Sondland.
Democratic Representative Ro Khanna sits on the Oversight committee. He said Bolton could explain three things:
- the extent of President Trump's knowledge on withholding military aid to Ukraine
- Bolton's own warnings to the president
- and President Trump's awareness of arranging a meeting with his Ukrainian counterpart to open a political investigation.
President Trump fired Bolton in September over disputes on how to handle foreign policy issues.