ABC News White House correspondent Jonathan Karl says his sources tell him that Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's anticipated report on the special counsel's investigation into Russian election meddling and possible collusion between President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE's campaign and Moscow is “almost certain to be anti-climactic.”

"There have been expectations that have been building, of course, for over a year," Karl told "This Week" host George Stephanopoulos on Sunday. "But people who are closest to what Mueller has been doing, interacting with the special counsel, caution me that this report is almost certain to be anti-climactic."

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"If you look at what the FBI was investigating in that New York Times report, you look at what they were investigating, Mueller did not go anywhere with that investigation," Karl continued. "He has been writing his report in real time through these indictments and we have seen nothing from Mueller on the central question of, was there any coordination, collusion, with the Russians in the effort to meddle in the elections? Or was there even any knowledge on the part of the president or anybody in his campaign with what the Russians were doing, there’s been no indication of that."

The New York Times reported last Friday that the FBI opened an investigation into whether Trump was working on behalf of Russia in 2017. According to the Times, the probe was prompted by Trump's dismissal of former FBI Director James Comey James Brien ComeyTrump jabs at FBI director over testimony on Russia, antifa Graham: Comey to testify about FBI's Russia probe, Mueller declined invitation Barr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' MORE.

Trump, however, called the report "insulting" during an interview on Saturday with Fox News.

"I think it's the most insulting thing I've ever been asked,” Trump told Fox News host Jeanine Pirro when asked if he had ever worked on behalf of Russia. “I think it's the most insulting article I've ever had written.”

The insight from Karl, who has also covered Capitol Hill, the Pentagon and State Department during his 15 years at ABC News, came just days after NBC News reported that Mueller's report is expected to be released in March.

Trump has repeatedly chastised the Mueller investigation, often referring to it as a "witch hunt."

In 2018, Trump tweeted about the Russia investigation as it relates to his 2016 campaign on 310 occasions.