United States President Joe Biden delivered a fiery news conference on the final day of the NATO summit in Washington, DC, as he sought to dispel concerns about his age and continued ability to lead.

“I’ve got to finish this job because there’s so much at stake,” Biden told a group of reporters.

Still, the Democrat, 81, misspoke on several occasions in the question-and-answer section, raising further concerns about his performance.

Biden is currently in a heated race for a second term in the White House. But his poll numbers have faltered after a dismal performance in the inaugural 2024 presidential debate, where he stumbled and stuttered opposite his Republican rival Donald Trump.

In the aftermath, a growing chorus of Democrats have called for Biden to drop out of the race, making room for a younger candidate to be the party’s nominee.

But Biden’s supporters framed Thursday’s NATO news conference — delivered on the third and final day of the summit — as a platform for the Democratic leader to show vigour and strength to the international community.

“My schedule has been full bore. Where has Trump been? Riding on his golf cart?” Biden said.

The stakes of the news conference were high for Biden. Earlier on Thursday, the number of congressional Democrats publicly pushing Biden to exit the race grew to 11.

Hours before the briefing, US Representative Hillary Scholten of Michigan became the 10th House Democrat to call for Biden to end his bid for re-election. On Wednesday, Senator Peter Welch of Vermont also called on Biden to suspend his campaign.

Amid the intense scrutiny, Thursday’s news conference came to be informally known as the “big boy” news conference, a moniker that made the rounds online and in late-night comedy ahead of the event.

At the White House earlier this week, Press Secretary Karine Jean-Pierre appeared to embrace the name, crediting it to Justin Sink from the publication Bloomberg.

However, she emphasised the serious nature of the speech, saying the president aimed to show the “unprecedented strength of our alliance” with NATO.

How did it go? Here are the key takeaways from Biden’s news conference.

A pre-speech fumble

Even before the speech started, Biden got off on the wrong foot.

Less than an hour before the news conference was scheduled to start, Biden introduced his Ukrainian counterpart Volodymyr Zelenskyy by the name of his battlefield adversary, Russian President Vladimir Putin.

“And now I want to hand it over to the president of Ukraine, who has as much courage as he has determination. Ladies and gentlemen, President Putin,” Biden said, gesturing to Zelenskyy.

But Biden quickly caught himself, recovering with a joke. “President Putin? He’s gonna beat President Putin!”

Zelenskyy, for his part, laughed off the gaffe. Several world leaders came to Biden’s defence, including French President Emmanuel Macron and German Chancellor Olaf Scholz.

“Slips of tongue happen, and if you always monitor everyone, you will find enough of them,” Scholtz told the press at the summit.

Since 2022, Russia has led a full-scale invasion of Ukraine, a prominent topic in this week’s NATO summit.

NATO Secretary-General Jens Stoltenberg, for instance, pledged that the war-torn country was on an “irreversible path to membership” in the military alliance, despite sabre-rattling from Russia.

And Biden himself announced a “historic donation of air defence equipment for Ukraine” in an earlier speech on Tuesday, at the start of the summit.

Speech takes aim at Trump’s criticism of NATO

The news conference opened after a delay, with Biden arriving at the podium with a “hey buddy” and noticeable throat-clearing.

But as he launched into prepared remarks, Biden took square aim at his Republican rival Trump.

The former Republican president has long been an outspoken critic of NATO, arguing that the US shoulders a disproportionate amount of the costs for the alliance.

Media reports also indicate that, behind closed doors, Trump has repeatedly threatened to withdraw the US from NATO, potentially destabilising the alliance.

“NATO grew out of the wreckage of World War II,” Biden said. “The idea was to create an alliance of free democratic nations that would commit themselves to a compact of collective offence. Staying together, they knew we would all be safer.”

But he said Trump would undermine that collective safety. “Every American must ask herself or himself: Is the world safer with NATO? Are you safer? Is your family safer? I believe the American people know the answer to all those questions is yes.”

Biden also implied that Trump, if re-elected, would fail to uphold Article 5 of the NATO treaty, which requires member states to defend one another if attacked.

“He’s already told Putin — and I quote — do whatever the hell you want,” he said. “But I made it clear: A strong NATO is essential to American security, and I believe the obligation of Article 5 is sacred.”

Bumps in the Q&A segment

At the end of his prepared remarks, Biden announced he had a list of reporters to call on in the question-and-answer segment of the news conference.

His performance grew slightly more uneven as he took repeated questions about his ability represent the Democratic Party in the upcoming election.

Biden has long struggled with a stutter, which emerged in several responses he gave to reporters.

But in one particularly noticeable flub, he accidentally swapped the name of his vice president, Kamala Harris, with that of Trump.

“I wouldn’t have picked Vice President Trump to be vice president if she wasn’t qualified to be president. So let’s start there,” Biden said.

It was a moment that Trump himself quickly seized upon on social media. He also mocked Biden’s stutter: “Crooked Joe: ‘I’m following the advice of my commander-in-chief … my … my … my …’”

Nevertheless, Biden was defiant in response to criticisms about his age and capacity to lead at the news conference.

“I think I’m the most qualified person to run for president,” he said. Of Trump, Biden added, “I beat him once, and I will beat him again.”

When asked how he would reassure the American public, Biden responded: “The best way to assure them is the best way to assure myself. And that is: Am I getting the job done?”

Biden acknowledges other Democratic contenders

Still, while Biden held fast to his position as the presumptive nominee for the Democratic Party, he acknowledged there were other contenders who could potentially do the job.

“There are other people who could beat Trump, too. But it’s awful hard to start from scratch,” Biden said.

The Democrat also offered warm words to Vice President Harris, his running mate and a figure often invoked as a possible replacement, should he step away from the race.

“This is a hell of a prosecutor. She was a first-rate person, and in the Senate, she was really good. I wouldn’t have picked her unless I thought she was qualified to be president,” Biden remarked.

“From the very beginning, I made no bones about that. She is qualified to be president. That’s why I picked her.”

As the news conference wound to a close, reporters continued to press the president about what it would take for him to step away from the race: Could his advisers say anything that would dissuade him?

“No, unless they came back and said there’s no way you can win,” Biden responded, before dropping to a whisper: “No one’s saying that. No poll says that.”

US election casts a shadow

However Biden’s performance on Thursday is received, the tight race for the White House has cast a long shadow over this week’s NATO summit, with allies expressing both concern and ambivalence.

For his part, Stoltenberg, the outgoing NATO secretary-general, called the NATO alliance “resilient”, despite concerns that a Trump presidency could weaken the alliance.

“Often there have been concerns about whether new governments, new political parties, will support NATO,” Stoltenberg said on Thursday. “And of course, in democracies, you don’t have any guarantees.”

Earlier in the week, Zelenskyy acknowledged that “everyone is waiting for November” to see how the US election pans out — including Russian President Putin.

But he encouraged world leaders to act before then, regardless of the outcome.

“It’s time to step out of the shadows, to make strong decisions work, to act and not to wait for November or any other month,” Zelenskyy said in his speech at the Ronald Reagan Institute on Tuesday.

The election, scheduled for November 5, will see Biden and Trump face off in a rematch of the 2020 race. After the speech, Biden is scheduled to campaign in the swing state of Michigan on Friday.