Standing side-by-side with Vladimir Putin, US President Donald Trump refused to blame the Russian leader for meddling in the US 2016 election, casting doubt on the findings of his own intelligence agencies and sparking a storm of criticism.
On a day when he faced pressure from critics, allied countries and even his own staff to take a tough line, Mr Trump spoke not a single disparaging word in public about Russia on any of the issues that have brought relations between the two powers to the lowest ebb since the Cold War.
Instead, he denounced the "stupidity" of his own country's policy, especially the decision to investigate election interference following the conclusions drawn by USintelligence agencies.
A prosecutor announced an indictment three days ago of Russian spies for hacking into Democratic Party networks.
Mr Trump's handling of a joint news conference in Helsinki stirred a wave of condemnation in the United States, where the White House has struggled for months to dispel a suggestion that Mr Trump was unwilling to stand up to Mr Putin.
His performance was denounced as "treasonous" by a former CIA chief and US Senator John McCain called meeting with Mr Putin a "tragic mistake," although some other Republicans were more cautious.
Asked if he believed US intelligence agencies, which concluded that Russia interfered in the 2016 election in an effort to help him defeat Democratic candidate Hillary Clinton, he said he was not convinced.
"I don't see any reason why it would be" Russia, Mr Trump said. "President Putin was extremely strong and powerful in his denial today."
In one response, the Director of National Intelligence Dan Coats, a Trump nominee approved by Congress, said in a statement: "We have been clear in our assessments of Russian meddling in the 2016 election and their ongoing, pervasive efforts to undermine our democracy, and we will continue to provide unvarnished and objective intelligence in support of our national security."
Hours after the Helsinki summit, Mr Trump tweeted, "I have GREAT confidence in MY intelligence people."
Before the summit even began, Mr Trump blamed his own country for the deterioration in relations.
"Our relationship with Russia has NEVER been worse thanks to many years of US foolishness and stupidity and now, the Rigged Witch Hunt!" he said on Twitter.
The Russian foreign ministry tweeted back: "We agree".
At the news conference, Mr Trump was invited by reporters to offer any criticism of Russia but he repeatedly declined.
Asked if Russia was at all to blame for the poor ties, he said, "I hold both countries responsible. I think the US has been foolish. We’ve all been foolish," he said, before veering into discussion about his election victory.
"I beat Hillary Clinton easily and frankly we beat her ...we won that race and it’s a shame that there can be even a little bit of a cloud over it," he said.
Mr Trump's warm words for Russia were a marked contrast from the past week when he repeatedly rebuked traditional US allies at a summit of NATO and during a visit to Britain.
Asked if Mr Putin was an adversary, he said, "Actually I called him a competitor and a good competitor he is and I think the word competitor is a compliment."
Mr Trump also refrained from publicly criticising Russia's 2014 seizure of Ukraine's Crimea region, another geopolitical win for Mr Putin against Western efforts to isolate him.
Mr Putin spoke of the importance of the two countries working together and praised Mr Trump, at one point interrupting the news conference to give the US president a soccer ball following the recent World Cup in Russia.
Asked whether he had wanted Mr Trump to win the 2016 election and had instructed officials to help him, Mr Putin said, "Yes I did," although he denied any interference, saying the allegations were "complete nonsense."
Mr Putin suggested US investigators could possibly travel to Russia to participate in questioning Russians accused by Washington of US election meddling as long as Russian investigators would be allowed to do the same with US spies operating in Russia, an idea Mr Trump's critics dismissed as ludicrous.
Republican Senator Lindsey Graham said Mr Trump's performance would send a message of "weakness" to Moscow.
"Missed opportunity by President Trump to firmly hold Russia accountable for 2016 meddling and deliver a strong warning regarding future elections. This answer by President Trump will be seen by Russia as a sign of weakness and create far more problems than it solves," Mr Graham said on Twitter.
Arizona Senator Jeff Flake, a frequent Trump critic, said: "I never thought I would see the day when our American President would stand on the stage with the Russian President and place blame on the United States for Russian aggression. This is shameful."
The Republican head of the US Senate Foreign Relations Committee, Bob Corker, said Mr Trump's comments at the joint news conference made the United States look like a "pushover."
US House of Representatives Speaker Paul Ryan, the top congressional Republican, took a more tempered approach but insisted that Mr Trump "must appreciate that Russia is not our ally."
Former CIA chief John Brennan went further, suggesting Mr Trump should be removed from office.
Mr Brennan tweeted: "Donald Trump’s press conference performance in Helsinki rises to & exceeds the threshold of 'high crimes & misdemeanors.' It was nothing short of treasonous. Not only were Trumps comments imbecilic, he is wholly in the pocket of Putin. Republican Patriots: Where are you???"
Top House Democrat Nancy Pelosi wrote on Twitter, "Every single day, I find myself asking: what do the Russians have on @realDonaldTrump personally, financially, & politically? The answer to that question is that only thing that explains his behavior & his refusal to stand up to Putin."
Senate Democratic Leader Chuck Schumer called for a bipartisan effort to "ratchet up" sanctions on Russia.
The summit capped a trip abroad during which Mr Trump accused NATO allies of failing to spend enough on their militaries and embarrassed British Prime Minister Theresa May by saying she refused to take his advice about how to negotiate Britain's exit from the EU.
He referred to the European Union itself as a "foe" in trade and repeatedly criticised it.
In some of the strongest words yet reflecting the unease of Washington's traditional allies, Germany's foreign minister said Europe could no longer rely on the United States.
"To maintain our partnership with the USA we must readjust it," Heiko Maas told the Funke newspaper group. "The first clear consequence can only be that we need to align ourselves even more closely in Europe."