AMNA NAWAZ: Welcome to the "NewsHour."

Today, in the Oval Office, President Biden convened his military and national security leaders for a briefing on the war in Ukraine, which took a devastating turn overnight.

Russian airstrikes struck a village in the eastern region of Kharkiv, killing more than 50 civilians, according to Ukrainian officials.

It is the most deadly attack in months.

And it comes at a moment when critical assistance from the U.S. is running out.

White House correspondent Laura Barron-Lopez and national security correspondent Nick Schifrin are at the table with me for an update.

And good to see you both.

Laura, just yesterday, President Biden expressed concern about securing some of that additional assistance for Ukraine.

What is the White House plan for getting that aid right now?

LAURA BARRON-LOPEZ: The president plans to give a speech in the coming weeks, Amna, where he is going to lay out the stakes.

He's going to essentially try to send a signal to foreign allies, foreign adversaries, but also domestically, that the U.S. needs to be in this, that the U.S. needs to continue its support of Ukraine.

And White House Press Secretary Karine Jean-Pierre was asked today about the urgency behind more aid for Ukraine.

KARINE JEAN-PIERRE, White House Press Secretary: We can go a bit longer, a bit longer, but it's not the long-term solution.

So the big piece of this right now is that we need Congress to keep their promise, to keep the promise that they made to Ukrainians.

LAURA BARRON-LOPEZ: And so I talked to a number of people today about this, essentially, two things, Amna.

One source close to the White House told me that what they want to hear from the president is a timeline and a big declaration for urgency, that this can't be something that is kicked down the road.

That's something that a senior Senate Republican aide also said that they agreed with.

And I also spoke to Senator Tim Kaine, a Democrat of Virginia, who sits on the Senate Foreign Relations Committee.

And he said that he wants Biden to lay out the stakes, but also not to necessarily just ask for Congress -- a vague request from Congress, that he wants Biden to say what exactly the White House wants in terms of the longer term, so into 2024, not the next 45 days, not to the end of the year, but well beyond that.

AMNA NAWAZ: So, Nick, what is the situation when it comes to funding in Ukraine?

How long can they last without additional funding?

NICK SCHIFRIN: The overall, simple answer to that, Amna, is not very long.

We just got back from the front in Southern Ukraine, and the situation is incredibly difficult.

We saw special forces units like this, and we saw ammunition shortages up and down the front, a lot of rationing by Ukrainian soldiers.

And that was even before the political chaos in Washington right now prevents the next package from passing.

Now, some U.S. officials believe Ukrainians are actually firing too much.

But the bottom line, long term, Ukraine cannot continue to fight the way it has been fighting unless U.S. levels of support remain at the levels they have been.

Now, the immediate term, let's look at the math.

Administration officials tell me they have about $5.6 billion of ammunition and weapons that they can draw down, draw down funds from existing stocks.

But here's the real number, $1.6 billion.

That's the number of replenishment funds that they would give to the military services for sending all those weapons to Ukraine.

And here's another number, zero dollars.

That is long-term military assistance known as the Ukrainian Security Assistant Initiative.

That is why you see the alarm from the administration right now.

AMNA NAWAZ: Laura, Nick referenced that political chaos here.

There is no full-time speaker in the U.S. House of Representatives right now, and there is a speaker race unfolding in real time.

How does that impact the potential for funding for Ukraine right now?

LAURA BARRON-LOPEZ: It impacts it a lot.

So it's incredibly important who the speaker is.

And, so far, we have two declared candidates, one that's considering.

Those candidates are majority leader in the House Republican Conference Steve Scalise, Judiciary Chairman Jim Jordan, and the head of the Republican Study Committee, Kevin Hern.

And so when you look at their grades on where they lie on support for Ukraine, the Republicans for Ukraine outside group has graded them based on their votes.

Scalise has a B.

Congressman Jim Jordan has an F. Congressman Hern has an F. And so when also asked about the potential for more Ukraine aid recently, Jim Jordan threw cold water on it.

REP. JIM JORDAN (R-OH): I have been clear all along.

Why should we be sending American tax dollars to Ukraine when we don't even know what the goal is?

No one can tell me what the objective is.

And so until you can tell me the goal, I don't think we should continue to send money there, particularly when we have the problems we have on our border.

LAURA BARRON-LOPEZ: So, talking to Democrats like Senator Tim Kaine, they read -- they see Jordan's comments and they say that isn't necessarily a hard no.

So, potentially, what could happen is that the Senate and a bipartisan group in the Senate tries to piece together a larger Ukraine aid package with some border security funding in it.

And they think that if they're able to do that, then they could potentially get, whether it's a Speaker Jim Jordan or a Speaker Steve Scalise, and their Republican Conference on board with that with some border security.

Now, if those House Republicans try to add on anything that would restrict refugee applications or asylum-seeker applications, go beyond just basic funding for the border and law enforcement down there, then, of course, they're going to meet resistance.

AMNA NAWAZ: Nick, what is the U.S. strategy moving forward for Ukraine?

NICK SCHIFRIN: Look, Ukraine has failed to push Russia out of Ukraine, and they failed to change Putin's calculus.

It still remains the same.

And some U.S. officials are telling me they doubt Ukraine can make any progress, frankly, in the next few weeks or the next few months.

So if the current strategy of providing weapons that the U.S. and the West have been willing to provide so far is not producing battlefield gains, and the level of support will probably go down, what's the administration going to do?

You have one option, go big, provide weapons systems that you have not yet provided to Ukraine, like long-range fires known as ATACMS.

You could go small, send less expensive weapons, send ammunition and smaller systems to make that $1.6 billion last longer.

But what they are unwilling to do, at least publicly, Amna, is Plan B, to even talk about any kind of negotiated settlement, because they think even talking about that with their allies would force or pressure Ukraine to concede.

And that is not their policy, at least right now.

AMNA NAWAZ: Amna Nawaz, Nick Schifrin, Laura Barron-Lopez, thank you so much for your reporting.

LAURA BARRON-LOPEZ: Thank you.

NICK SCHIFRIN: Thank you.