House Intelligence Chairman Adam Schiff Adam Bennett SchiffSchiff to subpoena top DHS official, alleges whistleblower deposition is being stonewalled Schiff claims DHS is blocking whistleblower's access to records before testimony GOP lawmakers distance themselves from Trump comments on transfer of power MORE (D-Calif.) said President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE’s former national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE is a “very important” witness in the ongoing impeachment probe.

Schiff added on ABC's "This Week" that Bolton has emerged from testimony others have given during closed-door depositions as a key witness.

“Obviously he has very relevant information and we do want him to come in and testify,” Schiff added.

"John Bolton is a very important witness...and we do want him to come in and testify," Rep. Adam Schiff tells @ThisWeekABC, adding that he predicts the White House may to try to block any possible testimony by Bolton. https://t.co/BURjYQzzys pic.twitter.com/5eV3nwlyfk — This Week (@ThisWeekABC) October 27, 2019

But the chair of the House Intelligence Committee indicated the White House may try to block Bolton from testifying.

He said the White House has tried to obstruct the investigation and witnesses coming in.

“My guess is they're going to fight us having john bolton in,” Schiff said. ADVERTISEMENT

The White House’s “obstruction” is one reason Schiff said he is hesitant to give a timeline of when the House will hold public hearings.

“We will be doing public hearings and I think we'll be doing them soon,” Schiff said.

“I don't want to give precise timing because, in part, we’re struggling with the White Houses's continuing efforts to obstruct our investigation,” he added.

The witness depositions have so far been limited to members of three House committees involved in the inquiry.