The Justice Department is through with special counsel Robert Mueller's investigation of alleged Russian interference in the 2016 election, Attorney General William Barr will tell senators Wednesday, according to prepared remarks released Tuesday night.

"With the completion of the Special Counsel's investigation and the resulting prosecutorial decisions, the Department's work on this matter is at its end aside from completing the cases that have been referred to other offices," according to Barr's prepared remarks for his testimony before the Senate Judiciary Committee.

Mueller declined to conclude whether President Donald Trump committed obstruction, according to a version of his report redacted by the Justice Department. And apart from prosecutions of other figures that are already underway, that's the end of the matter for the Justice Department, Barr says.

"From here on, the exercise of responding and reacting to the report is a matter for the American people and the political process," he says. "As I am sure you agree, it is vitally important for the Department of Justice to stand apart from the political process and not to become an adjunct of it."

Congressional Democrats indicated that Barr will likely come under sharp questioning in his testimony Wednesday and in his scheduled testimony before the House Judiciary Committee on Thursday. Barr has threatened to skip the House hearing because of his concerns over its format.

In an echo ofcomments made Tuesday night by Rudy Giuliani, Trump's personal attorney, Barr indicates in his prepared remarks that because Mueller didn't reach a conclusion on the president's involvement, that question has also been settled.

"The Special Counsel was, after all, a federal prosecutor in the Department of Justice charged with making prosecution or declination decisions," he says.

"Once a prosecutor has exhausted his investigation into the facts of a case, he or she faces a binary choice: either to commence or to decline prosecution," he says, adding: "The appointment of a Special Counsel and the investigation of the conduct of the President of the United States do not change these rules."

Giuliani made a similar point in an interview with NBC News after it was disclosed that Mueller sent Barr a letter objecting to his characterization of the special counsel's report, saying Barr's summary had created public confusion.

"If he didn't want confusion, he should have made a decision," Giuliani said. "He was made special counsel to make decisions, and the fact he didn't says to me (that Trump) was innocent."

While Barr says the Justice Department's involvement has concluded apart from prosecutions that are underway, he has said separately that he is "reviewing the conduct" of the FBI's Russia investigation in summer 2016.

The Justice Department's inspector general will release a report on the FBI's use of the Foreign Intelligence Surveillance Act in the case, he told a House Appropriations subcommittee on April 9.

The FBI is part of the Justice Department.