The U.S. Justice Department on Sunday released a four-page initial summary of Special Counsel Robert Mueller's 22-month-long investigation of Russia's interference in the 2016 presidential election.

“The special counsel's investigation did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 U.S. presidential election,” U.S. Attorney General William Barr wrote in a letter summarizing his “initial review” of Mueller's report.

Barr said he and Deputy Attorney General Rod Rosenstein concluded the evidence produced under Mueller's investigation “is not sufficient to establish that the president committed an obstruction-of-justice offense. Our determination was made without regard to, and is not based on, the constitutional consideration that surround the indictment and criminal prosecution of a sitting president.”

Barr said he and Rosenstein, who initially oversaw Mueller's probe, came to that determination after reviewing Mueller's findings, consulting Justice Department officials and lawyers, and applying the “principles of federal prosecution that guide our charging decision.”

The special counsel's office itself did not draw a conclusion about whether Trump's conduct constituted obstruction of justice, leaving unresolved what Mueller's team described as “difficult issues” concerning the president's actions. Barr's summary noted Mueller's report “sets out evidence on both sides of the question.”

Barr wrote in the summary: “The special counsel states that 'while this report does not conclude that the president committed a crime, it also does not exonerate him.'”

The Justice Department declined to publish the entirety of the Mueller report, the length of which has not been revealed. The release of the topline findings, which were provided to Congress, will only fuel demands that more information be released.

U.S. House Democrats are pushing for the release of the entire Mueller report, and a new lawsuit, filed Friday evening in Washington, contends Mueller's report must be disclosed under the federal Freedom of Information Act.

U.S. House Judiciary Chairman Jerrold Nadler, D-New York, said Sunday that House leaders would “absolutely” consider taking their fight for the full report to the U.S. Supreme Court. “That transparency is key,” Nadler said in an appearance on the NBC News program “Meet the Press.” “America needs answers as to what's been going on.”

In his letter Sunday, Barr indicated he would withhold sensitive information related to grand jury proceedings from a subsequent report to Congress. But Barr also reiterated that he intends to release as much as he can under the law, regulations and DOJ policies and said he has requested Mueller's assistance to identify all of that information “as quickly as possible.”

Nadler said on Twitter after the report was released: “There must be full transparency in what Special Counsel Mueller uncovered to not exonerate the President from wrongdoing. DOJ owes the public more than just a brief synopsis and decision not to go any further in their work.”

After receiving the letter Sunday, Nadler described the Justice Department's final decision-making as “very concerning” and said the House Judiciary Committee would call Barr to testify in the “near future.”

Some legal scholars have predicted the White House could attempt to assert executive privilege to block a broader release of Mueller's report.

The disclosure of Mueller's report doesn't end investigations involving Trump and others in his orbit. Federal prosecutors in New York are investigating the Trump inaugural committee, and other criminal prosecutions, including one against longtime Trump confidante Roger Stone, are playing out in court.

Sarah Sanders, the White House press secretary, said in a statement Sunday afternoon: “The special counsel did not find any collusion and did not find any obstruction. AG Barr and DAG Rosenstein further determined there was no obstruction. The findings of the Department of Justice are a total and complete exoneration of the president of the United States.”

Justice Department policy has long rejected the notion that a sitting president can be indicted. Legal scholars, however, for months now have debated this policy.

“Nearly everyone concedes that any such policy would have to permit exceptions. The familiar hypothetical of a president who shoots and kills someone in plain view clinches the point,” Harvard Law School professor Laurence Tribe wrote at the blog Lawfare in December.

Ken Starr, the independent counsel who led the Bill Clinton investigation, has taken the view that a sitting president cannot be charged.

“As we all peer into our respective crystal balls, and speculation abounds, we will do well to return to first principles. That means, in this case, accepting that the special counsel cannot seek an indictment, and must remain quiet,” Starr wrote recently at The Atlantic.

Mueller's principal conclusions are posted below: