NATO summit becomes Biden's biggest test of his mental stamina: What Joe, 81, needs to do to prove he can lead for four more years on the world stage

President Joe Biden faces a trial of his stamina pinch nan commencement of nan NATO acme connected Tuesday, wherever voters successful America and leaders from overseas will beryllium watching really he holds up aft his car-crash statement pinch Donald Trump.

The three-day fittingness trial will statesman Tuesday evening erstwhile Biden, 81, marks nan 75th day of nan organization. It will proceed done meetings and a meal pinch world leaders connected Wednesday and accumulate successful a property convention connected Thursday. 

Any stumble could summation calls among Democrats for him to exit nan statesmanlike race. A beardown capacity will statement up his statement he is tin of handling nan job.

Kurt Volker, a erstwhile US ambassador to NATO, said overseas leaders will get successful Washington looking for reassurance successful Biden personally but besides successful America's committedness to NATO. 

'Is it going to beryllium President Biden? Is he tin of that? Is he going to tally for reelection, is he going to get reelected? If so, what does that look like?' Volker told CNN connected Monday.

National Security Council spokesperson John Kirby said nan president didn't request to reassure friends pursuing nan debate. 

'We're not picking up immoderate signs of that from our friends astatine all,' he said Monday. 'Quite nan contrary, nan conversations that we're having pinch them successful advance, they are excited astir this summit. They are excited astir nan possibilities.' 

The gathering of nan leaders from nan 32 NATO countries — positive Pacific partners Australia, Japan, New Zealand and South Korea, arsenic good arsenic Ukraine — is expected to beryllium 1 of Biden's past appearances astatine an world forum earlier Election Day.

It besides comes earlier nan Republican National Convention successful Milwaukee adjacent week. 

Biden besides has taken in installments for nan description of NATO. Both Finland and Sweden person joined successful nan aftermath of Russia's February 2022 penetration of Ukraine. 

But, successful a reminder of his age, Biden is nan only caput of authorities who was live during NATO's founding. 

Biden has made 'restoring America's spot successful nan world' a awesome argumentation level aft Donald Trump's years of isolationist policy.

He cited his overseas argumentation grounds arsenic a logic he should stay his party's nominee.

'I expanded NATO. I solidified it,' Biden said connected MSNBC connected Monday. 'I made judge that we're successful a position wherever we person a conjugation of group of nations astir nan world to woody pinch China, pinch Russia. With everything that is going connected successful nan world. We're making existent progress.'

But leaders request reassurance he is up for nan job. 

'I deliberation this NATO acme successful Washington is an important infinitesimal for Joe Biden, he really has to show that he is pinch it, he's fresh to proceed to lead not only nan United States of America but nan NATO alliance,' erstwhile NATO Deputy Secretary-General Rose Gottemoeller told CNBC. 'And truthful we will spot successful coming days conscionable really good nan U.S. president does.' 

Trump, meanwhile, has suggested that successful a 2nd word he would not take sides NATO friends who didn't salary their afloat dues -  2% of their respective GDP. The erstwhile president besides has questioned nan magnitude of assistance to nan Ukraine.

During nan three-day meeting, Biden is expected to endorse caller assistance for Ukraine. 

He besides will clasp bilateral meetings pinch Ukrainian President Volodymyr Zelensky and caller British Prime Minister Keir Starmer.