AMNA NAWAZ: We turn now to the Middle East.

It's day 19 of the Israel-Hamas war, and Israel continues a heavy air assault on Gaza, as Palestinian groups fire rockets at Israel.

But there are new signs that an Israeli ground invasion may not be imminent after all.

Nick Schifrin begins our coverage.

NICK SCHIFRIN: On the Gaza border, they are parked and poised for a fight, hundreds of thousands of Israeli soldiers readying and training to invade Gaza.

But the ground invasion appears to be on hold for now, Prime Minister Benjamin Netanyahu indicated tonight.

BENJAMIN NETANYAHU, Israeli Prime Minister (through translator): We are working to ensure the ideal conditions for our troops for the next operations.

NICK SCHIFRIN: The delay discussed by Netanyahu and President Biden, as the U.S. military wants the USS Eisenhower and air defense systems to arrive in the Middle East before the invasion begins.

Already, 21 American service members were injured in drone attacks last week that the U.S. blames on Iranian-backed munitions.

Today, President Biden warned Iran's supreme leader.

JOE BIDEN, President of the United States: My warning to the ayatollah was that, if they continue to move against those troops, we will respond, and he should be prepared.

NICK SCHIFRIN: But a delay in the ground invasion also buys time for negotiations to release more hostages, as Biden told Netanyahu.

JOE BIDEN: What I have indicated to him is that if that's possible to get these folks out safely, that's what he should do.

It's their decision, but I did not demand it.

NICK SCHIFRIN: But Israel refuses to halt its air campaign, and across the Gaza Strip, the most vulnerable victims continue to need desperate care.

Gaza health authorities controlled by Hamas say 17,000 have been wounded and more than 6,500 killed.

President Biden today cast doubt on those numbers.

JOE BIDEN: What they say to me is I have no notion that the Palestinians are telling the truth about how many people are killed.

I'm sure innocents have been killed, and it's the price of waging a war.

NICK SCHIFRIN: Mr. Biden also called out violence committed by Jewish settlers.

JOE BIDEN: I continue to be alarmed about extremist settlers attacking Palestinians in the West Bank that -- pouring gasoline on fire is what it's like.

NICK SCHIFRIN: The fire Gazans wants stopped is Israeli airstrikes.

Today, they lifted a pile of rubble that used to be a bakery, as the bombs continue to fall.

ASAD AL-BAIROTI, Gaza Strip Resident (through translator): The Israeli occupation has proven that it's incapable of achieving any of its goals.

NICK SCHIFRIN: And, yet again, Gazans run for safety, as if there was any safe place in this war.

For the "PBS NewsHour," I'm Nick Schifrin.