GEOFF BENNETT: Welcome to the "NewsHour."

The Biden administration suspended delivery of thousands of bombs to Israel, a rare move by a White House that has said its commitment to Israel is -- quote -- "ironclad."

Israel seized the Rafah Border Crossing from Gaza into Egypt on Monday and said it would invade Rafah city if Hamas does not release the hostages it holds by week's end.

AMNA NAWAZ: Criticism of the suspension from many Republicans and some Democrats was swift.

Speaker Mike Johnson and Senate Minority Leader Mitch McConnell co-signed a letter to the president denouncing the delay.

The Biden White House also delayed delivery to Capitol Hill of a congressionally mandated report on whether or not the Israeli military is adhering to international humanitarian law.

Secretary of Defense Lloyd Austin defended the weapons pause at a Senate hearing this morning, before being interrupted by pro-Palestinian protesters.

LLOYD AUSTIN, U.S. Secretary of Defense: We're going to continue to do what's necessary to ensure that Israel has the means to defend itself.

But, that said, we are currently reviewing some near-term security assistance shipments in the context of unfolding events in Rafah.

Some of the security assistance that we're providing to... PROTESTER: Free Palestine!

AMNA NAWAZ: Following all of this is our Nick Schifrin, who joins me here at the desk tonight.

Nick, good to see you.

NICK SCHIFRIN: Thanks, Amna.

AMNA NAWAZ: Let's just start with what exactly the administration has suspended here.

NICK SCHIFRIN: The administration froze the shipment of 3,500 American bombs to Israel.

These are weapons that were already congressionally approved, specifically 1,800 2,000-pound bombs, which Israel has used mostly in Northern Gaza.

You see the aftermath of one right there to target Hamas tunnels deep underground.

But these are the bombs that have caused the most civilian casualties because of their size and because they are unguided.

A senior administration official says -- quote - - "We are especially focused on the end use of the 2,000-pound bombs and the impact they could have in dense urban settings."

That is a reference to Rafah, where, of course, 1.2 million Gazans have fled in Southern Gaza.

And Israel is threatening to assault, as you were saying before, especially Rafah city.

Now, Israel has more than enough weapons, Amna, to be able to assault Rafah.

So this is not about readiness.

This is what one official tells me is a message.

And that message is being sent also because the U.S. is saying, if Israel does not go into Rafah, then there will not be further frozen shipments, not only those 3,500 bombs that we talked about already, but a separate shipment of Joint Direct Attack Munition, or JDAMs.

These are kits that turn unguided munitions into precision-guided munitions that Israel is also asking for.

But the U.S. is not blocking any defensive weapons -- that includes missile defense -- nor is it blocking recent appropriated financial -- foreign financial money for Israeli weapons.

In total, the U.S. has sent Israel billions of dollars since October the 7th.

But it's a major step for President Biden, who's criticized this idea in the past.

The fact is that this is the largest leverage that the U.S. has over Israel, the weapons.

AMNA NAWAZ: It's a major step.

So what's been the response, both here at home and overseas?

NICK SCHIFRIN: The Democrats who have called for the U.S. to use this leverage hailed this idea, but Republicans criticized it.

The chairs of the House Foreign Affairs and Armed Services Committee said they were -- quote -- "appalled" by the decision, and they said it weakens deterrence against Iran and Lebanese Hezbollah.

And a source briefed on the details tells me that -- quote -- "Israeli officials expressed deep frustration at the delay of the shipment and the U.S. briefings to the media on the matter, raising concerns that the move may jeopardize the hostage deal negotiations at a critical moment."

And that's what makes this moment so critical, Amna.

CIA Director Bill Burns is in the middle of trying to convince the Israelis to accept the hostage deal, as Israel threatens this week to go into Rafah if there is no hostage deal, and the president is faced with this major decision of whether to withhold weapons.

All of these three major points are intertwined, and they have major ramifications not only for the war, but the future of the U.S.-Israel relationship.

AMNA NAWAZ: A critical point, indeed.

Nick Schifrin, thank you, as always, for your reporting.

NICK SCHIFRIN: Thank you.