AMNA NAWAZ: The "News Hour" has learned that the United States is holding back weapons that the Biden administration and the last Congress marked for Ukraine.

This comes as Russia has made territorial gains in Ukraine in recent days and blasted the country with unrelenting drone and missile attacks.

Nick Schifrin is here now with more.

So, Nick, tell us what you have learned about these weapons that were scheduled to go to Ukraine.

NICK SCHIFRIN: The Trump administration has halted weapons that Ukraine was scheduled to receive that, but, as you said, Amna, were appropriated by last term's Congress and authorized by the Biden administration.

The list includes these weapons, Patriot air defense missiles, 155-millimeter artillery rounds, GMLR missiles -- those are fired by a multiple-launch rocket system -- surface-to-air Stinger missiles, and missiles fired by jets known as AIM-7 and Hellfire missiles.

Tonight, Deputy White House Press Secretary Anna Kelly tells me -- quote -- "This decision was made to put America's interests first following a Department of Defense review of our nation's military support and assistance to other countries across the globe.

The strength of the United States armed forces remains unquestioned.

Just ask Iran."

A separate U.S. official tells me that this decision was based on the Department of Defense readiness review, meaning that officials believe that sending these weapons to Ukraine would reduce the U.S.' ability to be ready for any contingency, of course, especially China.

AMNA NAWAZ: So, in terms of real-world impacts from the cutting off of these weapons, what do we know?

What could be the impact?

NICK SCHIFRIN: I have been asking Ukrainian officials to respond to this since last night, and they have all declined.

But they have made clear over time that they especially need air defense missiles.

Patriots alongside other air defense are used to defend key Ukrainian sites, as well as its population and cities, from what is daily attacked by Russia.

In fact, Ukraine says Russia launched more than 5, 400 drone attacks in June.

A new U.N. report says there's been a 37 percent rise in civilian deaths and injuries over the last six months.

The cuts will also affect Ukraine's military's ability to go on offense.

You see there are those GMLRS fired by Ukraine to target concentrations of Russian troops and key targets inside of Russia because they can fly 40 miles.

Take a listen to Major General David Baldwin.

He was recently the former adjutant general of the California National Guard, which has been training Ukrainian troops since before the full-scale invasion by Russia.

And he continues to go to Ukraine to assist Ukrainian defense firms.

MAJ. GEN. DAVID BALDWIN (RET.

), U.S. National Guard: The United States not sending those particular weapons systems will have a tactical effect on the battlefield.

But, really, the effect is more on the will and morale of the Ukrainian people.

If you want to negotiate a peace settlement, it's always better to negotiate from a position of strength.

And that position of strength comes by continuing for the United States and our Western allies to supply arms, aid and material to the Ukrainians so they can continue to fight this illegal aggression.

NICK SCHIFRIN: Baldwin says he understands the U.S. argument that is being made, the need to prioritize other theaters, especially China.

But he points out that the fight against Ukraine is now in the future.

And he says, while Ukrainian and European defense firms are trying to increase their production of weapons, that just takes time, especially for air defense.

MAJ. GEN. DAVID BALDWIN (RET.

): They're not quite ready, and they're certainly not ready to start producing super sophisticated weapons systems like Patriots.

The answer is unfortunately a tough one for the United States government.

I would recommend that they continue to support the Ukrainians, because that fight is happening right now.

That's a fight against tyranny right now, while we continue to tool up our defense industry and spend more money to increase our capacity to build capacity to later face the Chinese.

NICK SCHIFRIN: And that is the argument, Amna, that U.S. officials inside the government who did want these weapons to continue to go to Ukraine, that's the argument they have been making.

AMNA NAWAZ: So put all this in context for us, Nick.

We reported earlier that Russia's been making territorial gains in Ukraine in recent days.

What should we know about that?

NICK SCHIFRIN: Over the last few months, Russia says that it has seized about 360 miles inside Ukraine -- to give you a little context, that's about the size of Indianapolis -- over the last few months.

Today, pro-Russian officials in Luhansk claimed capture of that region in all of Eastern Ukraine.

That's not believed to be true, but it has been close.

Russia has made a lot of gains in that area.

Russia did recently capture their first village in Southern Ukraine, Dnipropetrovsk, and they have been massing tens of thousands of troops in Northeastern Ukraine near Sumy.

Now, this comes at great cost, Amna.

Thousands and thousands of Russian soldiers are dying or being wounded every week.

And analysts do say that Ukraine is largely holding out despite these pushes, despite this really summer offensive that Russia has begun to launch in Ukraine.

But Ukrainian officials warn that any cuts to weapons that they receive will challenge their ability to hold out, especially, especially air defense.

AMNA NAWAZ: Nick Schifrin, great reporting, as always.

Thank you very much.

NICK SCHIFRIN: Thank you.