The announcement that President Biden has secured a deal to allow aid into Gaza has been hailed as a humanitarian breakthrough — but it still faces steep hurdles to reach the Palestinians in need.

Biden told reporters Wednesday that up to 20 trucks of aid from Egypt would be allowed into the besieged enclave, once potholes along the road and damage from Israeli airstrikes were repaired. Humanitarian officials warned, however, that a host of issues have yet to be resolved before the lives of the besieged inhabitants of Gaza are improved.

“Okay, it’s something,” said Yousef Hammash, a father of two, by telephone from Gaza. “At least we have it. Now we have to have a truce to distribute it. How are they going to do it under bombardment?”

The Gaza Strip, which is ruled by Hamas, has been under Israeli blockade for 16 years, leaving most of its 2.3 million residents dependent on aid before the current conflict. Those deliveries stopped entirely when Israeli and Egyptian border crossings into Gaza were closed after the Oct. 7 attack by Hamas, and the territory’s health system is now on the verge of collapse as thousands of casualties pour into hospitals that no longer have enough medical supplies to treat them.

While fighting continues, single aid deliveries will lessen the crisis, but only fleetingly, experts say. “What is needed is consistent and unimpeded aid access into and within Gaza, not only for the entry of and safe passage of supplies but also for humanitarians to be able to undertake their work safely,” said Emma Beals, a nonresident fellow at the Middle East Institute specializing in aid to conflict zones.

The U.N’s emergency relief coordinator, Martin Griffiths, told CNN that aid “needs to go in at scale” from the start. “We need to start with a serious number of trucks going in, and we need to build up to the 100 trucks a day that used to be the case of the aid program going into Gaza,” he said.

But stringent conditions on the aid make any sustained pipeline of deliveries unlikely. U.S. officials said the aid would be strictly watched for any signs of diversion by Hamas militants. Speaking aboard Airforce One as he departed Israel, Biden told reporters that any such diversion would mean an immediate halt.

“If Hamas diverts or steals the assistance, they will have demonstrated once again that they have no concern for the welfare of the Palestinian people,” Biden said. “As a practical matter it will stop the international community from being able to provide this aid.”

Low level aid diversion is common in active war zones, and international donors have threatened to stop the flow of aid in countries such as Syria and Ethiopia, only after the practice becomes long-standing. But it is unusual for the threshold for diversion to be set so low even before the trucks depart from their warehouses.

“Aid diversion is a concern in any aid operation, and all efforts must be made to ensure that assistance goes only to civilians, but red lines around diversion must be proportionate to the challenges inherent in aid delivery,” Beals said.

More than 100 aid trucks were lined up Thursday in the Egyptian city of al-Arish, waiting for a greenlight to cross into Gaza.

But on the other side of the border, Palestinians said they struggled to understand why the initial deliveries would be so small — or how they would actually reach people.

Mohamed Zanoon, an independent photographer who was working to document the aftermath of Israel’s air raids, said that he was witnessing a “humanitarian catastrophe.” He has struggled to push from his mind the memories of children screaming beneath the rubble.

“Twenty trucks isn’t enough,” he said. “More than a million people need medical care in Gaza.”

One of the biggest questions remains whether fuel will be allowed on the trucks. Without its regular deliveries, Gaza’s last operational power plant went dark last week, robbing the enclave of regular electricity. Hospitals across Gaza have struggled to keep the lights on with diesel-powered generators, and doctors warn that a total blackout would be a death sentence for patients on life support, in the operating theater or to newborns in their incubators.

In recent days, the Palestinian Health Ministry has repeatedly called on gas station owners and “anyone who has any liter of diesel” to power the generators to contact them immediately.

Humanitarian officials say they have yet to secure guarantees that aid workers delivering the supplies will be protected from Israeli bombardment. The World Health Organization says that it has recorded 59 attacks on medical infrastructure since Oct. 7, killing 16 health care workers, wounding 28 more and pushing four hospitals entirely out of service.

Griffiths said that humanitarian officials have been engaged in “incredibly detailed negotiations” about what an aid program to southern Gaza would look like, and that relief workers need reassurance that they will be able to deliver aid consistently and reach people where they are, “in the places that they choose to be safe.”

But for many Palestinians, nowhere in Gaza feels safe. The Palestinian news agency WAFA reported Wednesday that Israeli warplanes had bombed five bakeries in different locations, killing dozens of people and injuring hundreds as they lined up to buy bread. Medics and aid workers have also been killed in their off-duty hours, sometimes as they left their places of work to check on their families.

“The streets are not safe, and the entire population is in need,” said Hammash, the father of two who fled from Gaza City to Khan Younis farther south. “Every day we have to do our challenging daily mission of getting bread and water.”

He had moved to Khan Younis after the Israeli military ordered the evacuation of more than 1 million civilians there ahead of intensified bombing raids. But the mass displacement has piled such strain on local resources that Hammash said he now knew people who were heading back to their original locations.

“Either you get bombed in the north or you die from hunger here,” he said.

Meg Kelly in Washington contributed to this report.