Heads of state from Europe and North America are confronting the prospect of the return of NATO skeptic Donald Trump as Biden tries to save his reelection campaign, which has been in a tailspin following a disastrous June 27 debate performance against Trump.

The president said his work at the summit, where NATO is celebrating 75 years, would be a good way to judge his continued ability to do the job. He points to his work rallying NATO members in its stiff response to Russia's invasion of Ukraine as a prime example of his steady leadership and among the reasons he deserves another four years in the White House.

"Our allies are looking for U.S. leadership," Biden said in an MSNBC interview Monday. "Who else do you think can step in here and do this? I expanded NATO. I solidified NATO. I made sure that we're in a position where we have a coalition of ... nations around the world to deal with China, with Russia, with everything that's going on in the world. We're making real progress."

Biden is in a blitz to persuade voters, Democrats and donors that he's still up to the job. He's been making his case on the campaign trail, in a defiant letter to Democratic lawmakers and during friendly media interviews over the last several days. Still, he faces skepticism from some longtime allies.

Six Democratic House members have publicly called on Biden to quit his campaign, other lawmakers in private conversations have urged him to step aside, and several high-profile donors have raised concerns about his viability in the race.

The White House hopes to display to wobbly Democrats that Biden still has what it takes during what's expected to be a busy few days of formal summit meetings, sideline chats with leaders, long diplomatic dinners and receptions, and a summit-ending press conference.

Several senior administration officials who spoke on condition of anonymity to discuss internal conversations say the president displays a strong grasp of the broader issues -- Russia's invasion of Ukraine, the threat posed by China -- but on specific and incremental actions that countries or groups may take when it comes to these conflicts, Biden has appeared to be at worst confused or has not seemed to have a keen grasp on how to handle them.

However, the officials say there isn't -- at least not yet -- a crisis in confidence over Biden's general mental state.

The summit will give Biden his first chance to meet face-to-face with new British Prime Minister Keir Starmer. Biden called Starmer last week to congratulate him on his win and plans to host him Wednesday for talks at the White House.

The Labour Party leader had no concerns about Biden's mental acuity during their phone call, according to a spokesman for the prime minister who spoke on condition of anonymity to discuss the private call.

The gathering of the leaders from the 32 NATO countries -- plus Pacific partners Australia, Japan, New Zealand and South Korea, as well as Ukraine -- is expected to be one of Biden's last appearances at an international forum before Election Day and comes before next week's Republican National Convention in Milwaukee.

Biden has sought to spotlight his commitment to the alliance while making the case to voters that Trump would turn his back on NATO if he were to return to the White House.

Trump has repeatedly criticized fellow NATO members who failed to meet an agreed-upon goal of spending at least 2% of gross domestic product on defense spending. European anxiety was heightened in February when Trump warned NATO allies in a campaign speech that he "would encourage" Russia " to do whatever the hell they want" to countries that don't meet defense spending goals if he returns to the White House.

Trump has criticized Biden for providing an "endless flow of American treasure" to Ukraine. The Republican more recently has expressed openness to lending money instead and has said Ukraine's independence is important to the United States.

Biden aides have pushed back, noting NATO's announcement last month that 23 of 32 member nations are hitting the alliance's defense spending target this year. Nine member nations were meeting the goal when Biden took office in 2021.

Biden also has taken credit for the expansion of NATO. Both Finland and Sweden have joined in the aftermath of Russia's February 2022 invasion of Ukraine.

"That's not by accident," White House national security spokesman John Kirby said. "That's because of leadership. That's because of a constant stewardship of the alliance and other partnerships around the world. The president's record speaks for itself."

NATO is expected to announce details of Ukraine's pathway to membership into the alliance during the summit. NATO, which is built around the foundational agreement that an attack on one member is an attack on all members, has maintained it will not bring Ukraine into the fold until after the conflict with Russia ends.

Kirby said leaders also will discuss efforts to stand up a coordination center in Germany to help train, equip and coordinate logistics for Ukraine forces for its expected eventual accession into NATO.

The U.S. and allies plan to unveil steps during the summit to strengthen Ukraine's air defenses and military capabilities to help it deter Russian aggression, Kirby said.

Ian Brzezinski, a senior fellow at the Washington think tank the Atlantic Council, said Biden needs to use the summit to "significantly reverse the impression" that he left with his poor debate performance.

"This is an immense opportunity for him to lead with vigor and energy, to underscore his commitment, the administration's commitment, for that matter Congress' commitment to the alliance and to underscore that he brings to the table the resolve that has made NATO so successful," Brzezinski said.

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Associated Press writers Matthew Lee in Washington and Jill Lawless in London contributed to this report.