Former assistant Watergate prosecutor Jon Sale said on Sunday that President Donald Trump should be very happy with what has so far been revealed from Special Counsel Robert Mueller’s report into Russian interference into the 2016 election – but warned that this is only “round one.”

Speaking on Fox News’ “America’s Newsroom,” Sale said that the summary of Mueller’s report that is expected to be released on Sunday by Attorney General William Barr could shed more light on what Mueller’s investigation turned up, but will most likely disappoint people looking for more details into any collusion between the Trump campaign and Russian officials in 2016.

“I think in round one, the president should be very happy,” Sale said. “But it’s only round one, and now where are we? We’re waiting for the attorney general to decide what his summary is going to be.”

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Sale added: “What [Barr] received from Mueller is, by regulation confidential…What I think he is going to release sometime today may disappoint us as I don’t think it’s going to be as detailed and give the underlying information everybody is waiting for.”

Mueller's investigation is known to have concluded without a recommendation for further indictments after having snared nearly three dozen people, senior Trump campaign operatives among them. The probe illuminated Russia's assault on the American political system, painted the Trump campaign as eager to exploit the release of hacked Democratic emails to hurt Hillary Clinton and exposed lies by Trump aides aimed at covering up their Russia-related contacts.

Mueller submitted his report to Barr instead of directly to Congress and the public because, unlike independent counsels such as Ken Starr in the case of President Bill Clinton, his investigation operated under the close supervision of the Justice Department, which appointed him.

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Mueller was assigned to the job in May 2017 by Deputy Attorney General Rod Rosenstein, who oversaw much of his work. Barr and Rosenstein analyzed Mueller's report on Saturday, laboring to condense it into a summary letter of main conclusions.

Barr said he wants to release as much as he can under the law. That decision will require him to weigh the Justice Department's longstanding protocol of not releasing negative information about people who aren't indicted against the extraordinary public interest in a criminal investigation into the president and his campaign.

The Associated Press contributed to this report.