House Democrats tell The Daily Beast they’ve been told Special Counsel Robert Mueller is willing to testify before them about his report on Russian interference in the 2016 election, but the Department of Justice has been unwilling to set a date for it to happen.

The impasse comes as lawmakers have grown increasingly frustrated over Attorney General Bill Barr’s handling of the release of the Mueller probe and as other Trump associates have declined to appear before congressional committees.

Shortly after it was reported on Tuesday night that Mueller had written and called Barr to complain that the attorney general had not fully represented the special counsel’s findings, House Judiciary Committee Chairman Jerry Nadler (D-NY) sent out a statement demanding both men appear before his committee and saying he had been stonewalled so far.

“The Attorney General has expressed some reluctance to appear before the House Judiciary Committee this Thursday,” Nadler said. “These reports make it that much more important for him to appear and answer our questions. The Department of Justice has also been reluctant to confirm a date for Special Counsel Mueller to testify.”

Nadler had sent a letter to DOJ following the department’s release of the Mueller Report asking that Mueller appear for questioning no later than May 23. Two sources familiar with the conversations said the Judiciary Committee has been in regular contact with DOJ about setting a date for Mueller’s testimony and that those conversations were still going on. Committee sources said it was their impression that Mueller was willing to testify to discuss his findings, though it was unclear whether that would take place in public or behind closed doors.

But the DOJ has, according to multiple sources, not agreed to a date, citing Mueller’s continued status as a department employee—since the special counsel serves under the attorney general.

A Department of Justice spokesperson did not return a request for comment.

Barr, likewise, has been resisting congressional hearings, though mainly because he objects to the structuring of the proposed questioning. His reluctance has frustrated Democrats on the Hill, though he is slated to appear before the Senate Judiciary Committee on Wednesday.

Last week, House Democrats held a caucus call in which they discussed their strategy for the Barr hearing and how to get the White House to cooperate on investigations. Subsequent conversations between senior members focused on whether impeachment proceedings were appropriate given Trump’s refusal to comply with subpoenas.