Mueller is less than two months into his investigation of possible coordination between the Trump campaign and the Russian government to influence the 2016 election, and his every move has come under scrutiny. President Trump has decried the probe as a "witch hunt," and he and his supporters have raised questions about whether Mueller and his hires can be impartial.
A Justice Department spokesman declined to comment.
Carr said Mueller has hired 16 lawyers to work with him. Together, the team is a formidable collection of legal talent with experience prosecuting national security, fraud and public corruption cases, arguing matters before the Supreme Court and assessing complicated legal questions.
Trump and his allies have pointed out that many are Democratic donors.
Seven special counsel team members have donated to Democratic campaigns — five of those to Hillary Clinton's — and their giving totals nearly $53,000, according to Federal Election Commission records. The others have not donated at all, the records show.
The special counsel's budget also could become a source of contention. Shortly before Mueller was appointed, Trump seemed to express disdain that tax dollars were being spent on the Russia investigation, writing on Twitter, "The Russia-Trump collusion story is a total hoax, when will this taxpayer funded charade end?" He will likely soon have specific dollar figures to pair with his tweets.
The regulation under which Mueller was appointed does not specifically detail how the special counsel must disclose expenses to the public. It requires only that Mueller "be provided all appropriate resources by the Department of Justice," that he submit a proposed budget within his first 60 days and that he make a budget request 90 days before the start of the fiscal year.
When Patrick J. Fitzgerald, at the time a U.S. attorney, was appointed as special counsel to investigate the leak of the identity of CIA Officer Valerie Plame, the U.S. Government Accountability Office audited his expenditure statements every six months and released them publicly.