Attorney General William Barr has provided only a glimpse of Special Counsel Robert Mueller's report on the inquiry into Russia's role in the 2016 U.S. election, with many details expected to emerge when the document is finally released.

Barr on March 24 sent a four-page letter to lawmakers detailing Mueller's "principal conclusions" including that the 22-month probe did not establish that President Donald Trump's 2016 campaign team conspired with Russia. Barr said he found insufficient evidence in Mueller's report to conclude that Trump committed obstruction of justice, though the special counsel did not make a formal finding one way or the other on that.

5 Things to Look for in Mueller's Trump-Russia Report

The attorney general told Congress he hopes to release the nearly 400-page report this week, with portions blacked out to protect certain types of sensitive information.

5 Things to Look for in Mueller's Trump-Russia Report

Here are five things to look for when the report is issued.

5 Things to Look for in Mueller's Trump-Russia Report

Perhaps the biggest political risk for Trump is the special counsel's supporting evidence behind Mueller's assertion that while the report does not conclude the Republican president committed the crime of obstruction of justice it "also does not exonerate him" on that point.

According to Barr's March 24 letter, Mueller has presented evidence on both sides of the question without concluding whether to prosecute. Barr filled that void by asserting there was no prosecutable case. But Barr's statement in the letter that "most" of Trump's actions that had raised questions about obstruction were "the subject of public reporting" suggested that some actions were not publicly known.

Democrats in Congress do not believe Barr, a Trump appointee, should have the final say on the matter. While the prospect that the Democratic-led House of Representatives would begin the impeachment process to try to remove Trump from office appears to have receded, the House Judiciary Committee will be looking for any evidence relevant to ongoing probes into obstruction of justice, corruption and abuse of power by the president or others in the administration.

Barr's comment that most of what Mueller probed on obstruction has been publicly reported indicates that events like Trump's firing of James Comey as FBI director in May 2017 when the agency was heading the Russia inquiry are likely to be the focus of this section of the report.

The report will detail indictments by Mueller of two Kremlin-backed operations to influence the 2016 election: one against a St. Petersburg-based troll farm called the Internet Research Agency accused of waging "information warfare" over social media; and the other charging Russian intelligence officers with hacking into Democratic Party servers and pilfering emails leaked to hurt Democratic candidate Hillary Clinton.

With those two indictments already public and bearing no apparent link to the president, the focus may be on what Mueller concluded, if anything, about other incidents that involved contacts between Russians and people in Trump's orbit. That could include the June 2016 meeting at Trump Tower in New York in which a Russian lawyer promised "dirt" on Clinton to senior campaign officials, as well as a secret January 2017 meeting in the Seychelles investigated as a possible attempt to set up a back channel between the incoming Trump administration and the Kremlin while Democrat Barack Obama was still president.

Any analysis of such contacts could shed light on why Mueller, according to Barr's summary, "did not establish that members of the Trump campaign conspired or coordinated with the Russian government in its election interference activities."

In the weeks before Trump's former campaign chairman Paul Manafort was sentenced in March to 7-1/2 years in prison mostly for financial crimes related to millions of dollars he was paid by pro-Russia Ukrainian politicians, Mueller's team provided hints about what their pursuit of him was really about.

Prosecutor Andrew Weissmann told a judge in February that an Aug. 2, 2016 meeting between Manafort and Konstantin Kilimnik, a consultant Mueller has said has ties to Russian intelligence, "went to the heart of" the special counsel's investigation.

The meeting included a discussion about a proposal to resolve the conflict in Ukraine in terms favorable to the Kremlin, an issue that has damaged Russia's relations with the West. Prosecutors also said Manafort shared Trump campaign polling data with Kilimnik, although the significance of that act remains unclear.