The Justice Department on Wednesday appointed former FBI Director Robert Mueller as a special counsel to oversee a federal investigation into potential coordination between Russia and Donald Trump's campaign during the 2016 presidential election.

The appointment gives Mueller, who led the FBI through the Sept. 11 terrorist attacks and served under presidential administrations of both parties, sweeping powers to investigate whether Trump campaign associates colluded with the Kremlin to influence the outcome in his behalf, as well as the authority to prosecute any crimes uncovered during the probe. The broad mandate, beyond any specific Trump-Russia connection, also covers "any matters that arose or may arise directly from the investigation."

Deputy Attorney General Rod Rosenstein, facing scathing criticism for authoring a memo that preceded the firing last week of James Comey as FBI Director, said in a statement that Mueller's appointment was "necessary in order for the American people to have full confidence in the outcome."

"What I have determined is that based upon the unique circumstances, the public interest requires me to place this investigation into the authority of a person who exercises a degree of independence from the normal chain of command," Rosenstein said in a statement.

The appointment came amid a growing Democratic outcry for someone outside the Justice Department to handle the politically charged investigation.

It followed the revelation Tuesday that fired FBI Director James Comey had written in a memo that Trump, in a February meeting in the Oval Office, had asked him to end an investigation into former national security adviser Michael Flynn. The White House has denied that account.

Mueller was appointed FBI director in 2001 by President George W. Bush and stayed on beyond his 10-year term at the request of President Barack Obama, ultimately retiring in 2013.

The Justice Department said Mueller has resigned from his job at a private law firm to take the job of special counsel.

As special prosecutor, Mueller will have all the same powers as a U.S. attorney, though he will still ultimately report to Rosenstein. Still, he is not subject to the day-to-day supervision of the Justice Department. He can keep the same investigators in place, or request new or additional staff including from outside the department.

He will request a budget that includes personnel.

Rosenstein appointed Mueller under a statute that has been used only once, in 1999, when John C. Danforth was appointed to investigate allegations of government wrongdoing in the siege at the Branch Davidian compound in Waco, Texas.

Danforth's investigation cost millions of dollars and included hundreds of interviews and a restaging of the final hours of the 51-day standoff with federal agents. He ultimately produced a 150-page report clearing then-Attorney General Janet Reno and other top government officials of any responsibility.

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