WASHINGTON — Special counsel Robert Mueller, announcing Wednesday he’s closing his office and returning to private life, said that his report found that a legal opinion barred him from charging a sitting president and that his probe did not exonerate President Donald Trump.

In his first public statement in two years, Mueller defended his most controversial decision — to not make a prosecutorial judgment on whether Trump criminally obstructed the investigation — and suggested that that determination is now up to Congress.

“As set forth in the report after that investigation, if we had confidence that the president clearly did not commit a crime we would have said so,” Mueller said, a direct contradiction of Trump’s claim the report completely “exonerated” him.

He also warned about Russia’s interference in U.S. elections, citing “the central allegation of our indictments that there were multiple systematic efforts to interfere in our election,” he said, “and that allegation deserves the attention of every American.”

Mueller, 74, the former FBI director and federal prosecutor, took no questions after his 10-minute statement at the Justice Department and said he expected this to be his only public statement. He told members of Congress seeking his testimony: “The report is my testimony.”

Mueller also repeated his report’s finding that Russia made many efforts to influence the 2016 U.S. election, but he concluded that “there was insufficient evidence to charge a broader conspiracy” by Trump and his campaign.

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Trump responded to Mueller’s remarks in a tweet: “Nothing changes from the Mueller Report. There was insufficient evidence and therefore, in our Country, a person is innocent. The case is closed! Thank you.”

Rep. Jerrold Nadler (D-Manhattan), chairman of the House Judiciary Committee, which would initiate an impeachment inquiry or process, said in Manhattan that Mueller’s statement showed that Trump and Attorney General William Barr are “lying” about Mueller’s findings.

“He did not exonerate the President of the United States of obstruction of justice,” Nadler said. “Obstruction of justice is a serious crime that strikes at the core of our justice system. And the Constitution points to Congress to take action to hold the president accountable.”

Senate Minority Leader Chuck Schumer (D-N.Y.), in Patchogue, called on Trump and Senate Republicans to provide more money to local election boards “so there’s no further collusion in 2020.”

The retiring special counsel spent more than a quarter of his address discussing his report’s reasoning after Barr and others questioned why he chose not to make a decision on whether Trump had obstructed the investigation.

Barr acted on that non-decision — and later before Congress criticized Mueller for it — to say the evidence Mueller gathered was insufficient to file obstruction charges.

But Mueller said he and his team “did not make a determination as to whether the president did commit a crime” because of “long-standing department policy” that is it “unconstitutional” to charge a president with a federal crime, as well as out of “fairness.”

“Charging the president with a crime was therefore not an option we could consider,” he said, saying that the department’s opinion further informed the handling of his obstruction probe.

“First, the opinion explicitly permits the investigation of a sitting president, because it is important to preserve evidence while memories are fresh and documents available,” Mueller said. “And second, the opinion says that the Constitution requires a process, other than the criminal justice system, to formally accuse a sitting president of wrongdoing.”

That process is impeachment, according to the opinion.

Asked about Mueller’s statement that the report did not clear Trump of criminal obstruction, White House Press Secretary Sarah Huckabee said, “If Bob Mueller determined that there was a crime, he would have had a moral obligation to report it. He didn't.”

Mueller also praised his team of lawyers, FBI agents, analysts and professional staff — derided by Trump as “angry Democrats” with an ax to grind — as “of the highest integrity.”

He also noted he and Barr had disagreed on Barr’s summary of the report, but said he appreciated that Barr made the report “largely public” and does not question his “good faith.”

Mueller’s comments, however, did not calm the storm over his 448-page report.

Democratic presidential contenders Sen. Cory Booker of New Jersey and Sen. Kirsten Gillibrand of New York, among others, urged the House to begin impeachment proceedings.

“It's time for Congress to begin impeachment hearings and follow the facts. Robert Mueller clearly expects Congress to exercise its constitutional authority and take steps that he could not,” Gillibrand tweeted.

But Trump campaign manager Brad Parscale said in a statement, “The case is now closed. Now it’s time to turn to the origins of the Russia hoax and get to the bottom of why the Trump campaign was spied on by the Obama-era DOJ and FBI.”

With David M. Schwartz and Laura Figueroa Hernandez