President Trump used a stage he shared with Russian President Vladimir Putin — in a Finnish palace packed with international journalists — to voice breathtaking doubts about the case against Moscow and renew his attacks on special counsel Robert S. Mueller III. (Pablo Martinez Monsivais/AP)

U.S. officials had only days earlier released some of the most detailed intelligence on Russia that America’s spies have ever allowed the public to see: information on bitcoin deposits, names of cyber-operatives even a description of a keyboard used to hack the 2016 U.S. election campaign. Then the nation’s top intelligence official warned that Russia’s cyber-intrusions were not only real but have continued unabated.

None of it has been enough to persuade President Trump to believe his government over the claims of the Kremlin.

In an astonishing repudiation of U.S. intelligence services and the American system of justice, Trump used a stage he shared with Russian President Vladimir Putin — in a Finnish palace packed with international journalists — to voice breathtaking doubts about the case against Moscow and renew his attacks on special counsel Robert S. Mueller III.

Questioned about Russia’s attack, Trump said, “I don’t see any reason why” Moscow would have even attempted to intervene in the 2016 campaign.

The intelligence community has concluded that the Russians conducted the operation to damage American democracy, help Trump and hurt Hillary Clinton, who has long been despised by Putin for questioning the legitimacy of his rule.

Challenged to condemn Russia’s actions and warn Putin against future interference, Trump spun into a recitation of counterclaims and conspiracy theories about supposedly missing computer servers and Clinton’s emails.

Asked whether he holds Russia accountable for any part of its attempts to undermine U.S. democracy, Trump said, “I hold both countries responsible . . . and I think we’re all to blame.”

Current and former U.S. officials were staggered by the spectacle, with some accusing Trump of having crossed a line into betrayal of his country.

Former CIA director John Brennan, who was among the first to warn that Russia was waging a campaign to help Trump, said in a posting on his Twitter account that the president’s “press conference performance in Helsinki rises to & exceeds the threshold of ‘high crimes & misdemeanors.’ It was nothing short of treasonous.”

Daniel Coats, the intelligence chief whom Trump treated as no more credible than Putin, issued a statement Monday saying that the nation’s spy agencies “have been clear in our assessments of Russian meddling . . . and their ongoing, pervasive efforts to undermine our democracy.”

The scorn Trump heaped on U.S. spy agencies was exceeded only by the attack he launched on Mueller and a probe that he called a “disgrace” and a “disaster for our country.” He was speaking of an investigation that has racked up indictments and guilty pleas against some of the top advisers to Trump during his campaign and presidency — as well as leveling charges against 26 Russians, including military intelligence officers, for their alleged role in hacking Democratic computer networks, witness tampering and spreading disinformation to impact the vote.

“The repeated accusation that the special counsel’s investigation is a ‘witch hunt’ is belied not only by the integrity and professionalism of the special counsel and his staff, but by their demonstrable and formidable accomplishments to date,” said David Laufman, a former chief of the Justice Department’s Counterintelligence and Export Control Section who had helped lead the Russia probe. “And to have lodged such an accusation on foreign soil, standing alongside the very individual believed to have sanctioned the 2016 assault on our electoral process, is a betrayal of the law enforcement and intelligence communities on whom we all depend to protect the national security of the United States.”

Deputy Attorney General Rod J. Rosenstein personally briefed Trump on the Russian hacking indictment before the president departed for Europe. When the charges against a dozen Russian military intelligence officers were announced Friday, by Justice Department officials who knew Trump would soon be meeting with Putin, Rosenstein delivered pointed remarks about the politicization of the probe.

“When we confront foreign interference in American elections, it is important for us to avoid thinking politically as Republicans or Democrats and instead to think patriotically as Americans. Our response must not depend on who was victimized,” Rosenstein said

The Russia probe was set in motion by the FBI in 2016 amid a flurry of contacts between Trump campaign officials and Russians with close ties to the Kremlin, all against the backdrop of Moscow’s hacking and the release of thousands of stolen emails on WikiLeaks.

Mueller, who was appointed after Trump fired former FBI director James B. Comey last year, has been tasked with uncovering the truth about Russia’s interference and delivered the most detailed picture of the Kremlin operation in an indictment filed late last week.

The document charged 12 Russian spies accused of carrying out covert assignments as part of the Kremlin’s interference campaign. It described how they used anonymous payment mechanisms to rent a computer server in the United States, disclosed the malware they used to rummage through Democratic Party networks, and traced some of the hackers’ steps back to the keyboards where they directed hacking operations and adopted phony identities.

Some of the disclosures were so staggering that former CIA officials said they could not recall U.S. spy agencies ever allowing the public — and therefore the Kremlin as well — to have such insight into their espionage capabilities.

But Trump made clear that he sees the consensus position of U.S. spy services as offset by Putin’s persistent denials, counterclaims clouded by too much ambiguity for the American president to make a judgment.

“I have great confidence in my intelligence people, but I will tell you that President Putin was extremely strong and powerful in his denial today,” Trump said.

Sen. Richard Burr (R-N.C.), chairman of the Senate Intelligence Committee, said it “has reviewed the 2017 [Intelligence Community] assessment and found no reason to doubt its conclusion that President Putin ordered an influence campaign aimed at the 2016 U.S. elections with the goal of undermining faith in our democratic process. . . . Any statement by Vladimir Putin contrary to these facts is a lie and should be recognized as one by the President.”

At several moments Monday, Trump seemed to nod approvingly as Putin disputed American claims against Russia. “Who is to be believed and . . . who’s not to be believed,” Putin said, a line that closely tracked Trump’s position.

At one point, Putin seemed to be mocking the United States — offering to help American investigators pursue their theories about Russian culpability, while imposing a condition that he knew the United States could never abide.

Putin said members of Mueller’s team could travel to Moscow and be permitted to witness Russian authorities question the defendants named in the latest U.S. indictment. “This kind of effort should be a mutual one,” Putin said, meaning that Russia would then expect to be granted entry to the United States to take part in questioning of CIA officers and others that the Kremlin suspects of interfering in Russian affairs.

Trump leaped at the proposal. “What he did is an incredible offer,” Trump said. “I think that’s an incredible offer.”

Trump made his statements in front of senior members of his national security team, including Secretary of State Mike Pompeo, who previously led the CIA. Many senior officials in the administration are baffled by Trump’s position but attribute it to his inability to accept any claim that might devalue his win over Clinton in the 2016 election.

He gave new credence to that theory Monday, launching repeatedly into unprompted discourses about the magnitude of his win. “That was a clean campaign. I beat Hillary Clinton easily. . . . And it’s a shame that there could be even a little bit of a cloud over it,” he said.

The stream of outbursts came as part of a summit that Trump has pursued since the moment he took office with the foreign leader he most frequently lavishes with praise.

Trump’s denials stretch back to before he was president and are now effectively “baked in” to his relationship with Putin, a former U.S. intelligence official said.

“He made it all about him and not Russia’s attack on our democratic system,” said another senior official, who was distraught over the spectacle of a U.S. president siding with an adversary power against his own intelligence leaders.

For some, the press conference was reminiscent of Trump’s comments after last summer’s protests in Charlottesville, in which Trump said that racist marchers and counterprotesters shared a measure of blame for the violence that ensued. Given the opportunity, with the world watching, to say once and for all that Russia was solely responsible for the election interference, Trump suggested that the story was more complicated, and refused to take a side.

Harris reported from Washington. Julie Tate, Ellen Nakashima and Matt Zapotosky contributed to this report.