STORY: Prime Minister Benjamin Netanyahu on Thursday said Israelis were ready to "fight with the fingernails."

It was a thinly-veiled rebuff to U.S. President Joe Biden, after Washington said it had paused a weapons shipment due to Israel's plans for a military operation in Gaza.

Biden warned Israel he will not support an invasion of the city of Rafah without adequate safeguards for the civilian population, as an estimated half of Gaza's 2.3 million residents have sought shelter there.

The paused shipment includes several thousand powerful aerial bombs, that the White House says are not suitable for warfare in densely-populated areas.

TOM COTTON: "It's now plain what we suspected all along. Joe Biden's defacto position is for a Hamas victory over Israel."

That pause provoked fiery criticism from Republicans in Congress, who characterized the holdup of a single weapons shipment as tantamount to the a betrayal of an ally. Here's Oklahoma Senator Tom Cotton:

"Joe Biden is threatening to withhold weapons for fighting in Rafah, therefore, Joe Biden objectively favors a Hamas victory over Israel."

The Pentagon dismissed the criticism from Senate Republicans, listing the massive amounts of military aid that has flowed from the U.S. to Israel, including missile defense capabilities.

PENTAGON SPOKESPERSON PAT RYDER: "As you know, we provided billions of dollars in security assistance to Israel..."

Last month, American forces assisted in shooting down hundreds of Iranian drones and rockets aimed at Israel.

Meanwhile, billions of dollars worth of U.S. weaponry remains in the pipeline for Israel, despite the delay.

Republican Senator Jim Risch told reporters on Thursday that the U.S. was planning to send tank rounds, mortars, armored tactical vehicles, and more.

In the wake the Oct. 7 attack where Hamas gunmen killed 1,200 people, by Israeli tallies, and seized more than 250 hostages, Biden pledged his "ironclad" support for Israel.

But the Israeli retaliation that has killed 35,000 people in Gaza, according to local health authorities, forced Biden into a difficult spot between supporting and ally and trying to limit the loss of life.

Biden had been pressed by international allies and many of his fellow Democrats at home to condition billions in U.S. aid to Israel due to the massive death toll from its Gaza assault.

And a U.S. official told Reuters those pressure came to a head on an April 4 phone call between the leaders after Israeli forces killed seven World Central Kitchen volunteers.

Biden gave Netanyahu an ultimatum: protect citizens and aid workers, or else U.S. policy would change.

And last week, the U.S. acted on it, pausing the delivery of 2,000-pound and 500-pound bombs.

In an interview with CNN Wednesday night, Biden said: "Civilians have been killed in Gaza as a consequence of those bombs and other ways in which they go after population centers."