GENEVA — Another American president might have been frustrated, or even angry.
Moments after spending more than three hours on Wednesday across a table from President Biden at their first summit, President Vladimir V. Putin of Russia delivered his usual list of grievances to reporters.
He denied Russian culpability for cyberattacks targeting U.S. interests, accusing the United States of carrying out more. He said America’s human rights record was worse than his country’s. And he accused the Biden government of a military buildup near Ukraine.
It was vintage Putin, and it seemed to reinforce the idea that the high-profile diplomatic exchange on the banks of Lake Geneva had done little to change a relationship that has deteriorated for years.
But if Mr. Biden was annoyed by his counterpart’s performance, there was no sign of it during his own subsequent news conference, or at a later conversation with reporters under the wing of Air Force One before he left Switzerland to conclude his eight-day, three-country diplomatic tour of Europe.
Mr. Biden’s response to his Russian adversary underscored a persistent feature of his presidency: a stubborn optimism that critics say borders on worrisome naïveté and that allies insist is an essential ingredient to making progress.
“The country has put a different face on where we’ve been and where we’re going — and I feel good about it,” Mr. Biden said before boarding his plane, chiding the news media for being too skeptical. “I mean, look, guys, I’m going to drive you all crazy because I know you want me to always put a negative thrust on things.”
The important thing, he said, is to “put on an optimistic front and optimistic face” while remaining realistic about the prospects for real change over the long run.
“If you were in my position, would you say: ‘Well, I don’t think, man, anything is going to happen. This is going to be really rough. I think it’s going to really be bad’?” Mr. Biden asked the reporters. “You’d guarantee nothing happens.”
Mr. Biden’s life has been filled with sorrow and disappointment, including the deaths of his wife and daughter as a young senator and the loss of his son Beau to cancer just as the older Mr. Biden was contemplating a run for the presidency. But despite the tragedies, much of his public life has been marked by a determination to see the positive where others don’t.
To listen to Mr. Biden at his news conference, one could easily conclude that the meeting with Mr. Putin had been a resounding success. The president noted an agreement with Russia to begin work on a new arms-control agreement. The trick, he said, is to figure out what his adversary’s interests are. In Mr. Putin’s case, he wants “legitimacy, standing in the world stage,” Mr. Biden said. “They desperately want to be relevant.”
That kind of unrestrained positivity has already opened him to the charge that he’s naïve, unwilling to see the reality staring at him across the table. It will also raise questions about whether he’s willing to confront looming challenges: Russia’s aggression at NATO’s eastern border, damaging cyberattacks from inside Russia and the country’s worsening human rights record.
But Mr. Biden’s approach is unlikely to change. He has tried to set an optimistic tone since he entered the Oval Office. He has pushed for bipartisanship on passage of his domestic agenda, even as many, if not most, of his allies in Washington are eager to abandon the courtship of Republicans amid growing pessimism that it will ever be consummated.
In his efforts to confront the coronavirus pandemic, he has regularly expressed a belief that Americans will emerge stronger and safer, while some health experts have been more cautious in their predictions. Mr. Biden can be the ultimate cheerleader, as he was in his first address to Congress.
“It’s never ever, ever been a good bet to bet against America, and it still isn’t,” he said that night.
In foreign policy, Mr. Biden is an old-school diplomat who places his faith in face-to-face conversations like the one he had with Mr. Putin on Wednesday and the many exchanges he had with other leaders at the Group of 7, NATO and European Union summits over the past week.
At the G7, as well as the NATO meeting, the president expressed his belief that allies once again had faith in the commitment of the U.S. government. Asked about concerns that European leaders worried about an eventual return of former President Donald J. Trump — or someone like him — Mr. Biden waved the concern aside.
When it comes to Russia, Mr. Biden and his top foreign-policy aides have insisted that they do not want a “reset,” a term that has come to represent the perceived naïveté of Mr. Biden’s Democratic predecessor, Barack Obama, in his dealings with Russia and Mr. Putin.
But Mr. Biden’s reflection on his own summit with Mr. Putin had the feeling of a kind of reset, at least in Mr. Biden’s telling. He went out of his way to insist that no threats had been made, no voices raised, just a “positive” exchange between two leaders who don’t trust each other yet.
“We didn’t have to trust somebody to get Start II,” he said, referring to the arms control treaty.
The only time that Mr. Biden raised his voice during his news conference in Geneva was when Kaitlan Collins, a CNN reporter, asked him why he was confident that Mr. Putin would change his behavior. Mr. Biden, who was walking out of the news conference, turned on his heels and lashed out.
“I’m not confident he’ll change his behavior. Where the hell — what do you do all the time?” he said. “I said: ‘What will change their behavior is if the rest of the world reacts to them and it diminishes their standing in the world.’ I’m not confident of anything; I’m just stating a fact.”
Ms. Collins followed up by challenging the president to justify his rosy outlook, citing Mr. Putin’s comments.
“If you don’t know that,” he snapped, “then you’re in the wrong business.”
It was a harsh response intended to push back against the cynicism that the president dislikes. But it was also a recognition of sorts by Mr. Biden that his optimistic approach is sometimes the target of criticism.
After a brief ride in the motorcade to the airport, Mr. Biden thanked supporters and then walked briskly over to the small group of reporters set to accompany him back to Washington.
Mr. Biden, referring to his comment to the CNN reporter, said he owed an apology: “I shouldn’t have been such a wise guy with the last answer I gave.”