Hours after the call, Israel announced new steps to boost Gaza aid. The White House said the measures 'must now be fully and rapidly implemented.'

President Joe Biden issued an ultimatum to Israel that U.S. support in the Gaza war depends on "immediate" steps to protect civilians and aid workers, the White House said Thursday.

Within hours of a tense call between Biden and Israeli Prime Minister Benjamin Netanyahu, the Israeli government said it would take new measures to increase aid to the devastated coastal enclave, including opening the Erez crossing from Israel into northern Gaza and the Ashdod port, and increasing aid deliveries from Jordan.

It was unclear if those steps would satisfy Biden. A National Security Council spokeswoman said Thursday night the steps "must now be fully and rapidly implemented."

"As the president said today on the call, U.S. policy with respect to Gaza will be determined by our assessment of Israel’s immediate action on these and other steps, including steps to protect innocent civilians and the safety of aid workers," spokeswoman Adrienne Watson said.

Biden spoke with Netanyahu three days after a team from celebrity chef José Andrés' World Central Kitchen aid group were killed in an Israeli drone strike in northern Gaza.

"President Biden emphasized that the strikes on humanitarian workers and the overall humanitarian situation are unacceptable," the White House said in a statement earlier Thursday. "He made clear the need for Israel to announce and implement a series of specific, concrete, and measurable steps to address civilian harm, humanitarian suffering, and the safety of aid workers."

Biden "made clear that U.S. policy with respect to Gaza will be determined by our assessment of Israel’s immediate action on these steps," the statement said.

Veteran U.S. diplomat Dennis Ross, now at the Washington Institute for Near East Policy, said Biden had given Netanyahu a clear ultimatum. "The president, in effect, is saying meet these humanitarian needs or I will have no choice but to condition (military) assistance," Ross said.

Monday's drone strike on the World Central Kitchen team marked the first time foreign aid workers, including one American citizen, have been killed in the six-month Israel-Hamas war, prompting a swift apology from Netanyahu and the Israeli military, and a condolence phone call by Biden to Andrés.

The deaths of foreign humanitarians, coupled with Andrés' celebrity status and popularity in Washington, appears to have shaken Biden administration at a time when surveys show that a majority of Americans no longer support Israel's war against Hamas.

"If we don't see the changes we need to see, there will be a change in our policy," Secretary of State Antony Blinken told reporters.

"In terms of concrete steps, what we are looking to see and hope to see here in the coming hours and days is a dramatic increase in humanitarian assistance getting in and additional crossings opened up," National Security Council spokesman John Kirby said earlier Thursday.

It wasn't clear what exactly the administration was threatening Israel with if it doesn't change its conduct in Gaza, but Biden's threat drew a swift reaction from some supporters of Israel in Congress.

"In this war against Hamas − no conditions for Israel," Sen. John Fetterman, D-Penn., wrote on social media.

"Instead of attacking our ally, Joe Biden should demand Hamas release the hostages," Sen. Tom Cotton, R-Ark., said on X, the former Twitter.

Biden pushes cease-fire and hostage release

The White House said Biden had pushed Netanyahu to conclude long-stalemated cease-fire negotiations with Hamas.

The president "underscored that an immediate ceasefire is essential to stabilize and improve the humanitarian situation and protect innocent civilians, and he urged the Prime Minister to empower his negotiators to conclude a deal without delay to bring the hostages home," the statement said.

Hamas holds more than 100 hostages taken in a stunning Oct. 7 rampage in southern Israel that killed 1,200. More than 32,000 people have died in Gaza since then, according to the Hamas-run health ministry, as Israeli forces seek to root out the Islamist militant movement.

Earlier on Thursday, an unnamed senior Hamas leader told Reuters that the group had rejected cease-fire proposals by regional diplomats.

"The Hamas leadership informed the Egyptian and Qatari mediators that what is being offered cannot be accepted, as it is a continuation of the stubborn Israeli position," the leader told Reuters.

Israel last month called Hamas' cease-fire demands "delusional."

Last month, the U.S. abstained on a U.N. Security Council resolution calling an immediate cease-fire and hostage release.

Humanitarian bloodbath

More than 200 aid workers, the vast majority of them Palestinians, have been killed in Israeli airstrikes and gunfire since the beginning of the war, officials say.

"This conflict has been one of the worst in recent memory in terms of how many aid workers have been killed," Biden said in the statement. "This is a major reason why distributing humanitarian aid in Gaza has been so difficult — because Israel has not done enough to protect aid workers trying to deliver desperately needed help to civilians."

Biden said he was "outraged and heartbroken" by the attack, which included one American, in a statement Tuesday.

Andrés said Wednesday that Israeli forces had targeted a World Central Kitchen convoy "systematically, car by car," after the team delivered tons of food aid to a warehouse in central Gaza.

On the very same day of the airstrikes which killed the aid workers, the Biden administration reportedly signed off on shipment of thousands more bombs to Israel, an attack that has drawn outrage around the world.

Three U.S. officials told the Washington Post the State Department approved the transfer of more than 1,000 MK82 500-pound bombs, over 1,000 small-diameter bombs and fuses for MK80 bombs. All the weapons transfers had been authorized by Congress years before the Oct. 7 attack on Israel that ignited the current war in Gaza, said the U.S. officials who spoke on the condition of anonymity to discuss sensitive arms deals.

'Constant fear' in Gaza

Speaking by phone from Rafah, on Gaza's border with Egypt, one humanitarian official told USA TODAY that only an end to the fighting would ensure an end to civilian and air worker deaths.

"A change in Israel's rules of engagement will mitigate some of the civilian toll, but the only way to guarantee the safety of civilians and humanitarians is through a permanent cease-fire," said Federico Dessi, the Middle East regional director for the aid group Humanity and Inclusion.

"People are in constant fear," Dessi said. "There is nowhere safe in Gaza. The threat of an offensive in Rafah is dangling over their heads."