Alan Dershowitz predicted that the special counsel Robert Mueller's report about the investigation into Russia's meddling in the 2016 US election would be "politically very devastating" for President Donald Trump.

Dershowitz, a Harvard law professor, said he did not think the investigation would result in criminal charges against the president.

Dershowitz is known as a frequent defender of Trump, and Trump has spoken highly of him, though Dershowitz has also criticized some of the president's policies.

The special counsel Robert Mueller's report on the Russia investigation is likely to be "politically very devastating" for President Donald Trump, said Alan Dershowitz, a Harvard law professor who has frequently defended Trump.

"I think the report is going to be devastating to the president," Dershowitz told ABC News' "This Week" on Sunday. "And I know that the president's team is already working on a response to the report."

Dershowitz said that he doubted the investigation into Russia's meddling in the 2016 US presidential election would result in criminal charges against Trump but that the results could still devastate the president.

"When I say devastating, I mean it's going to paint a picture that's going to be politically very devastating," Dershowitz said.

Read more: Here are the 2 topics Mueller drilled down on in his questions to Trump

Dershowitz said it was unlikely to result in charges against Trump because "collusion is not criminal," a defense that Trump and other supporters of the president have previously invoked.

But legal experts have said that while there is no "crime of collusion," there are many closely related crimes, including conspiracy to defraud the US.

Alan Dershowitz spoke to ABC News on Sunday about Robert Mueller's Russia investigation. ABC News

Dershowitz said he did not think Trump would be charged with what Dan Abrams, an ABC News legal analyst, described on "This Week" as "conspiracy to cooperate with an attempt to defraud the United States government."

"It's too much of a stretch," Dershowitz said.

Read more: New report reveals the behind-the-scenes battle between Trump's team and Mueller over a possible interview on the Russia investigation

He predicted that Mueller would "lay out the facts" and "leave it to Congress to decide whether that rises to the level of an impeachable offense."

Dershowitz said it was "a very hard question" to predict when the report would be made public, as Matthew Whitaker, Trump's new acting attorney general, has criticized the investigation, but that it "will be made public probably with a response alongside."

Trump has recognized Dershowitz as someone who often defends him, though Dershowitz has criticized some of the president's policies. Trump tweeted last year that Dershowitz's appearance on "Fox & Friends" to talk about the Russia investigation was a "must watch." And in an interview with The New York Times in December, he called Dershowitz "amazing."

Dershowitz has given blunt assessments of accusations against Trump. Last year, he described reports that Trump shared highly classified information with two Russian officials in the White House as "the most serious charge ever made against a sitting president."

He also said that multiple investigations into Trump's finances in New York were "the greatest threat" to Trump because he has "constitutional defenses" against Mueller's inquiry but not those probes.