Special Counsel Robert Mueller made his first public statement about his investigation into Russian interference in the 2016 presidential election Wednesday morning, saying that the investigation is formally closed and that he is resigning from the Department of Justice.

"I have not spoken publicly during our investigation," Mueller said. "I'm speaking out today because our investigation is complete."

Mueller also reiterated that Justice Department policy prohibiting the indictment of a sitting president meant that "charging the president with a crime was therefore not an option we could consider." He added that the Constitution requires a process other than through the criminal justice system to find a president guilty of a crime.

"It would be unfair to potentially accuse someone of a crime" knowing that the issue could not be resolved in the courts, Mueller said.

The special counsel found that there was significant interference by the Russian government in the 2016 election, but that the Trump campaign did not conspire with Russia to influence the election.

Although the special counsel did not reach a conclusion on whether Mr. Trump obstructed justice, the Mueller report did examine 10 "discrete acts" in which he may have done so. Attorney General William Barr and Deputy Attorney General Rod Rosenstein determined that Mr. Trump did not obstruct justice.

Mueller also said that he would not be speaking publicly again about the report.

"I hope and expect that this will be the only time I will speak to you about this matter," Mueller told reporters. He also said that while there were conversations about his testifying before Congress, "the report is my testimony."

"I would not provide information beyond that which is already public," Mueller said.

A senior White House official said that "the White House was notified" Tuesday night that Mueller might make a statement today.

Barr is in Alaska on Wednesday for a Native American roundtable on justice issues.

Mueller's statement comes after the Guardian published an excerpt from journalist Michael Wolff's new book, "Siege: Trump Under Fire," which claimed that there had been a draft version of a three-count criminal indictment against Mr. Trump compiled as early as March 2018. A spokesman for the special counsel, Peter Carr, flatly denied this reporting, which was attributed to "a source close to the Office of Special Counsel."

"The documents that you've described do not exist," Carr said.