WASHINGTON – In his first public comments on the Russia investigation, special counsel Robert Mueller pointedly refused to clear President Donald Trump of criminal wrongdoing but said charging him with obstruction was “not an option” because of Justice Department policy against prosecuting a sitting president.

In a 10-minute statement delivered from the Justice Department on Wednesday morning, Mueller defended the investigation he supervised, said it was unnecessary that he testify before Congress and announced that he was leaving the department and closing his office. His remarks largely echoed the text of the 448-page report he submitted in March, but this time, he delivered them himself, on camera and in public.

Mueller recounted his report’s overall findings, saying Russia launched a “concerted” effort to interfere with the election. “There were multiple, systematic efforts to interfere in our election, and that allegation deserves the attention of every American,” he said.

Mueller said the inquiry into Russia’s efforts was one of “paramount importance,” so investigators took seriously efforts by Trump and others to thwart their work. He said the department’s Office of Legal Counsel prohibited the prosecution of a sitting president, and his team of prosecutors was bound to follow that rule.

Mueller said that if prosecutors had confidence that the president clearly didn’t commit a crime, “we would have said that.”

Before leaving the podium, he offered a clearer signal to Congress that lawmakers have the power to make their own judgment about the president’s conduct even if he couldn’t bring criminal charges.

“The Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing,” Mueller said, describing the department’s rationale for why a president cannot be prosecuted. He did not directly identify that process, but he was referring to the daunting political exercise of impeachment.

Trump tweeted after the statement that nothing had changed from Mueller’s report.

“There was insufficient evidence and therefore, in our Country, a person is innocent,” Trump said. “The case is closed!”

Mueller’s final report described wide-ranging efforts by the Russian government to intercede in the 2016 election on Trump’s behalf but said investigators did not find sufficient evidence to establish a conspiracy with Trump’s campaign. Mueller made no decision on whether to press charges of obstruction of justice, despite detailing 10 episodes in which investigators said the president tried to thwart their work.

In his report and again Wednesday, Mueller framed that decision as being less about evidence than about the government’s rules for accusing the president of a crime.

Justice Department policy “clearly permits the investigation of a sitting president because it is important to preserve evidence while memories are fresh and documents are available,” Mueller said. “Among other things, the evidence could be used if there were co-conspirators who could now be charged.”

Mueller said that he would have nothing more to say on the subject, that the special counsel’s office was closing and that he was resigning from the Justice Department. If called to testify before Congress, he said, he would repeat only what was in his office’s final report.

White House spokeswoman Sarah Sanders said Mueller “is moving on with his life, and everyone else should do the same.”

Some Democrats call for Trump’s impeachment, but House leaders have not joined them. Speaker Nancy Pelosi, D-Calif., said she is “gravely disappointed” with officials at the Justice Department who misrepresented the report. She said 38 Democrats out of 238 in the House advocate impeachment, so six committees will continue to investigate Trump.

“We are legislating, we are investigating and we are litigating,” Pelosi said. “Nothing is off the table. But we do want to make such a compelling case, such an ironclad case, that even the Republican Senate, which at the time seems to be not an objective jury, will be convinced of the path that we have to take as a country.”

Other Democrats in the House were eager to take more aggressive steps. Rep. David Cicilline, D-R.I., who sits on the Judiciary Committee, said Wednesday that the next step is to open an impeachment inquiry to allow the collection of evidence and compel the attendance of witnesses.

Jimmy Gurule, a former assistant attorney general who is a law professor at the University of Notre Dame, said Mueller left wide open the question of whether Trump obstructed justice. He and others questioned whether the special counsel delivering that assessment in person would do much to change the political calculus in Congress.

“I think the voice in the House is going to get louder. There are going to be more calls for impeachment,” Gurule said. “But I don’t think it’s going to change any Republican views.”

Attorney General William Barr, who consulted with other lawyers at the department, decided at the end of Mueller’s investigation that no obstruction charges were warranted, even if they could be brought. Barr was confirmed near the end of the inquiry that had been overseen by Deputy Attorney General Rod Rosenstein, who appointed Mueller.

Barr has been criticized for his initial four-page summary of the report’s conclusions and for statements he made in releasing a redacted version of the report. Some of the criticism came in a letter in March from Mueller, who differed with the attorney general about Barr’s characterization of the special counsel’s principal findings.

Wednesday, Mueller acknowledged their differences but downplayed any lingering dispute, saying, “I do not question the attorney general’s good faith in that decision.”

Barr defended his handling of the report before the Senate Judiciary Committee. Trump said that the report completely exonerated him and that the investigation was a partisan witch hunt and attempted coup.

House Democrats were eager to hear from Mueller. The chairman of the House Judiciary Committee, Rep. Jerry Nadler, D-N.Y., has been negotiating for Mueller’s testimony at a public hearing. Nadler said Wednesday in New York that Mueller’s statement provided much of the information lawmakers needed to hear about substantial evidence of a Russian attack that benefited Trump.

“The president’s response to repeatedly lie to the American people and ignore all congressional subpoenas is immoral and unlawful,” Nadler said. “No one is above the law, and we will hold the president accountable.”

In response to a question about impeachment, Nadler said, “All options are on the table, and nothing should be ruled out.”

Senate Majority Leader Mitch McConnell, R-Ky., declared the Russia investigation “case closed.” The chairman of the Senate Judiciary Committee, Sen. Lindsey Graham, R-S.C., said Wednesday that Barr’s decision on obstruction was sound and that it would be the final word on the investigation.

Mueller said nobody in the administration told him whether to testify. He said he couldn’t say anything more publicly than what is included in the report.

“The work speaks for itself,” Mueller said. “The report is my testimony.”