AMNA NAWAZ: Welcome to the "News Hour."

President Biden is facing a high-pressure moment, preparing to hold his first solo press conference in several months at the NATO Summit in Washington.

It's a major public test for the president's reelection campaign as he faces questions over his stamina and his health.

GEOFF BENNETT: Earlier today, three of the president's top campaign advisers met with Senate Democrats behind closed doors to address concerns over his political future.

Some lawmakers expressed skepticism before and after the meeting.

QUESTION: What's the main objective in the room today?

To find consensus?

SEN. JOE MANCHIN (I-WV): To make sure the health and well-being of the president is able to be judged.

SEN. MICHAEL BENNET (D-CO): If things stay as they are, it's likely that Donald Trump will win the election and that we will lose the Senate and we will lose the House.

SEN. RICHARD BLUMENTHAL (D-CT): He has to continue to allay those concerns that have been expressed by the American people.

More than myself or my colleagues, the voters are what matter.

AMNA NAWAZ: And our White House correspondent, Laura Barron-Lopez, is at the NATO Summit and joins us now.

So, Laura, what has been the response from the Biden team to these latest calls from more lawmakers for him to step aside?

LAURA BARRON-LOPEZ: Amna, President Biden, some of his closest advisers went up to the Hill today to meet with senators.

That included campaign chair Jen O'Malley Dillon and two of his top advisers in the White House, Steve Ricchetti and Mike Donilon.

Now, we -- senators were pretty mum coming out of that meeting.

They weren't really offering much, but we know that what those advisers were trying to communicate to the senators was that they still have a pathway to 270, multiple pathways, they say.

And we got a taste of what the Biden administration -- excuse me -- what the Biden campaign's argument is in a memo that Jen O'Malley Dillon, the campaign chair, sent out to supporters today and also sent internally to the campaign staff.

And in that memo, O'Malley Dillon says that there was no sea change after the debate and that they have multiple pathways to 270.

She said -- quote -- "Right now, winning the blue wall states, Michigan, Wisconsin and Pennsylvania, is the clearest pathway to that aim.

But we also believe that the Sun Belt states are not out of reach.

The consensus being across internal and public polling is that everything remains within the margin of error for the president and that he can ultimately still win this."

AMNA NAWAZ: Meanwhile, Laura, every moment for the president becomes kind of high-stakes test.

You're about to go walk in to this press conference he's going to give at NATO at during this summit, the first time he's taken questions from a group of reporters since the debate.

What do you expect to happen in there?

LAURA BARRON-LOPEZ: This is a really critical moment for the president, Amna.

This is a high-stakes press conference, one that the White House calls a big boy press conference.

And it's -- he's expected to take a number of questions on his own from reporters.

He's going to be met with a pretty probably aggressive press corps that is going to be asking about why he thinks he should remain in this race, especially as more and more House lawmakers, in particular, House Democrats, come out saying that they think he should step aside.

A number of House Democrats were texting me today saying that they think that, no matter how he does in this press conference, that more and more Democrats are going to call on him to step aside, especially as NATO allies leave.

AMNA NAWAZ: So, Laura, after this press conference, what else can we expect to see from the Biden White House, from the Biden campaign, as they work to quiet these concerns?

LAURA BARRON-LOPEZ: President Biden's team just keeps maintaining that he is in this and that he is not exiting the race, despite all of the lawmakers that are saying that they think that he should step aside and donors that privately are saying that they think he should step aside.

They say that the vast majority of Democrats are still behind him, including the delegates.

So the president is going to be campaigning more, they said.

They put him out there more in the past week.

They said they're going to continue doing that.

And they're also putting him out with the press more.

He is going to have a sit-down with NBC on Monday that a number of Democrats tell me they're also going to be watching closely.

AMNA NAWAZ: All right, that is our White House correspondent Laura Barron-Lopez joining us from the NATO Summit.

Laura, thank you.

LAURA BARRON-LOPEZ: Thank you.