The Department of Justice has instructed two top deputies to former Special Counsel Robert Mueller not to testify before the House Intelligence and Judiciary Committees, putting a deal that lawmakers made with prosecutors in jeopardy.

Both a senior congressional official and a Justice Department official confirmed to the New York Times that the department had told the two deputies, Aaron Zebley and James L. Quarles III, that it did not want them to talk to the House committees investigating President Donald Trump.

Both Zebley and Quarles have left the DOJ and are now private citizens, so the government technically cannot stop them from testifying. The opinion of the department may make the two lawyers reluctant to comply with the House and provide them with a plausible reason to not appear before the panels.

The two men had tentatively agreed to appear before the House committees during a closed-door meeting to provide information about possible obstructions of justice committed by the president, as they were heavily involved in Mueller’s probe. Zebley, who is considered to be Mueller’s closest associate, served as the prosecutor’s chief of staff when he was F.B.I. director and functioned in a similar role during the special counsel’s investigation, coordinating the legal teams. House Democrats hope that he will be able to provide details during the private session that Mueller would not be able to share during his scheduled public hearing.

Attorney General William Barr told reporters that he would support Mueller if he decided to back out of his testimony and that he would direct the DOJ to prevent the House from subpoenaing any of Mueller’s associates.

Rep. Adam Schiff (D-California), Chairman of the House Intelligence Committee, said that Barr’s actions were unsurprising. “Earlier when he said it is completely up to Bob Mueller whether he testifies, he was counting on Bob Mueller not wanting to testify and not be compelled to,” Schiff told reporters. “But now I think his real motivation is exposed. He is nothing if not transparent and transparently the president’s agent.”