Deputy Attorney General Rod Rosenstein on Wednesday defended Special Counsel Robert Mueller’s investigation into the Trump campaign and its possible collusion with Russia during the 2016 election, calling the probe “appropriate and independent.”

In an interview with The Wall Street Journal, the Justice Department’s second-in-command disputed the idea that the special counsel’s investigation was “rigged,” as President Trump has so often described it.

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“People are entitled to be frustrated, I can accept that,” Rosenstein said in regard to the investigation.

“But at the end of the day, the public will have confidence that the cases we brought were warranted by the evidence and that it was an appropriate use of resources,” Rosenstein said.

The deputy attorney general appointed Mueller as special counsel in May 2017 after Trump fired James Comey as FBI director.

Rosenstein told the Journal the investigation has already exposed Russian attempts to infiltrate the presidential election.

Four former Trump campaign associates — Michael Flynn, Paul Manafort, Richard Gates and George Papadopoulos — have been charged so far. The special counsel has also charged two others, as well as 13 Russian nationals and 12 Russian intelligence officers.

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Rosenstein said he “committed I would ensure the investigation was appropriate and independent and reached the right result, whatever it may be. … I believe I have been faithful to that.”

It was reported by Bloomberg earlier Wednesday that Mueller’s office is preparing to deliver core findings of its investigation shortly after next month’s midterm elections.

The outlet, citing two anonymous U.S. officials, reported that Mueller is finalizing the conclusions related to the questions on whether President Trump’s campaign colluded with Russia and whether he took any actions that could constitute obstruction of justice.

Asked about the timeline, two sources close to the president's legal team told Fox News they also believe the Mueller probe is "winding down."

Fox News’ Kaitlyn Schallhorn and Lukas Mikelionis contributed to this report.