WASHINGTON — The Justice Department is seeking to discourage Robert S. Mueller III’s deputies from testifying before Congress, potentially jeopardizing an agreement for two of the former prosecutors to answer lawmakers’ questions in private next week, according to two government officials familiar with the matter.
The department told the House Intelligence and Judiciary Committees last week that it was opposed to the testimony and had communicated its view to the two former members of Mr. Mueller’s team, Aaron Zebley and James L. Quarles III, according to a senior congressional official familiar with the discussions. A Justice Department official confirmed that account and said that the department had instructed both men not to appear.
It is unclear what effect the Justice Department’s intervention will have on the men’s eventual appearances, but it raises the prospect that a deal lawmakers thought they had struck last month for testimony from Mr. Mueller, the former special counsel, and the two prosecutors could still unravel.
Both Mr. Zebley and Mr. Quarles have left the Justice Department and are now private citizens, meaning that the department most likely cannot actually block their testimony. But the department’s view — depending on how strongly it is expressed — could have a chilling effect on two longtime employees and give them cover to avoid testifying.
Spokesmen for both the House judiciary and intelligence panels declined to comment on Tuesday.
The Wall Street Journal first reported that Mr. Zebley and Mr. Quarles were in talks to appear in private before the committees and that the Justice Department had objections.
Democrats on the two House panels reached a deal late last month, after weeks of negotiations, for testimony from the prosecutors. Under the terms outlined by lawmakers and officials familiar with the discussions, Mr. Mueller agreed to testify publicly under subpoena on July 17 in back-to-back, time-limited hearings before the Judiciary and Intelligence Committees.
But Mr. Zebley and Mr. Quarles tentatively agreed to make limited appearances as well to answer questions from lawmakers from the two committees behind closed doors. Those private appearances are still in flux, the congressional official said, speaking on the condition of anonymity to talk about discussions that were intended to be private.
Lawmakers are eager to hear from both men, who were among Mr. Mueller’s top deputies on the team he built for his investigation into Russia’s 2016 election interference and President Trump’s attempts to impede the inquiry.
Mr. Zebley is considered Mr. Mueller’s closest associate. He served as his chief of staff when Mr. Mueller was F.B.I. director, and he functioned in a similar role in the special counsel’s office, coordinating the team working for Mr. Mueller and as a go-between with the Justice Department. He is intimately familiar with most aspects of the investigation, and in a private session could probably add details and context that Mr. Mueller would not in public.
Mr. Quarles, a seasoned Washington legal hand, worked as a Watergate prosecutor and at Mr. Mueller’s former firm, WilmerHale, before he joined the special counsel’s team. Mr. Quarles was heavily involved in the team’s investigation into whether Mr. Trump’s attempts to impede investigators constituted obstruction of justice, and he was the lead intermediary with the White House.
The Justice Department’s private communications appear to be consistent with public comments made in recent days by Attorney General William P. Barr, who on Monday accused Democrats of trying to “create some kind of public spectacle” rather than find new facts.
In an interview with The Associated Press, Mr. Barr said that the Justice Department would support Mr. Mueller if he wanted to back out. And he said that the department would seek to block any attempt by House Democrats to subpoena members of Mr. Mueller’s prosecutorial team.
Representative Adam B. Schiff, Democrat of California and the chairman of the Intelligence Committee, said he was not surprised that Mr. Barr and his team would try to intervene, as they have with other congressional witnesses.
“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,” Mr. Schiff told reporters. “But now I think his real motivation is exposed. He is nothing if not transparent and transparently the president’s agent.”