Senators are warned that if they agree to call Bolton to testify or try to access his book manuscript, the White House will block him, beginning a weekslong court battle over executive privilege and national security.

The debate over witnesses received a jolt Sunday when The New York Times reported that Trump told his national security adviser he wanted to maintain a freeze on military aid to Ukraine until it launched political investigations into his rivals.

The president is accused of trying to get Ukraine to announce an investigation into his political rival while holding back congressionally approved military aid as leverage.

The House prosecutors, followed by the president’s lawyers, each have 24 hours spread out over 3 days to present their cases.