U.S. Vice President Kamala Harris on Sunday demanded Palestinian militant group Hamas agree to an immediate six-week ceasefire while forcefully urging Israel to do more to boost aid deliveries into Gaza, where she said innocent people were suffering a "humanitarian catastrophe."

In some of the strongest comments by a senior leader of the U.S. government to date on the issue, Harris pressed the Israeli government and outlined specific ways on how more aid can flow into the densely-populated enclave where hundreds of thousands of people are facing famine, following five months of Israel's military campaign.

"Given the immense scale of suffering in Gaza, there must be an immediate ceasefire," Harris said at an event in Selma, Alabama. "There is a deal on the table, and as we have said, Hamas needs to agree to that deal. Let's get a ceasefire."

"People in Gaza are starving. The conditions are inhumane and our common humanity compels us to act...The Israeli government must do more to significantly increase the flow of aid. No excuses," she said.

On Sunday, a Hamas delegation had arrived in Cairo for the latest round of ceasefire talks, billed by many as the final possible hurdle for a truce, but it was unclear if any progress was made. Israeli newspaper Yedioth Ahronoth's online version reported that Israel boycotted the talks after Hamas rejected its demand for a complete list naming hostages who are still alive.

Washington has insisted the ceasefire deal is close and has been pushing to put in place a truce by the start of Ramadan, a week away. A U.S. official on Saturday said Israel has agreed on a framework deal.

An agreement would bring the first extended truce of the war, which has raged for five months so far with just a week-long pause in November. Dozens of hostages held by Hamas militants would be freed in return for hundreds of Palestinian detainees.

One source briefed on the talks had said on Saturday that Israel could stay away from Cairo unless Hamas first presented its full list of hostages who are still alive. A Palestinian source told Reuters that Hamas had so far rejected that demand.

After the Hamas delegation arrived, a Palestinian official told Reuters the deal was "not yet there." There was no official comment from Israel.

In past negotiations Hamas has sought to avoid discussing the wellbeing of individual hostages until after terms for their release are set.

In other diplomatic moves, Israeli war cabinet member Benny Gantz will meet Harris at the White House on Monday and U.S. Secretary of State Antony Blinken in Washington on Tuesday. U.S. envoy Amos Hochstein will visit Beirut on Monday to pursue efforts to de-escalate the conflict across the Lebanese-Israeli border.

Gunfire and chaos"

The death last week of more than 100 Palestinians approaching an aid truck in Gaza has captured the severe humanitarian crisis in the densely-populated enclave, an incident Harris recalled during her speech.

"We saw hungry, desperate people approach aid trucks simply trying to secure food their family after weeks of barely no aid reaching northern Gaza and they were met with gunfire and chaos," Harris said.

Israel said on Sunday its initial review of the incident had found that most of those killed or wounded had died in a stampede. Military spokesman Daniel Hagari said Israeli troops at the scene initially fired only warning shots, though they later shot at some "looters" who "approached our forces and posed an immediate threat."

Muatasem Salah, a member of the Emergency Committee at the Ministry of Health in Gaza, told Reuters the Israeli account was contradicted by machine gun wounds.

In her comments, Harris laid out specific ways on how the Israeli government can allow more aid into Gaza. "They must open new border crossings. They must not impose any unnecessary restrictions on the delivery of aid. They must ensure humanitarian personnel, sites and convoys are not targeted, and they must work to restore basic services and promote order in Gaza, so more food, water and fuel can reach those in need."

Under pressure at home and abroad, the Biden administration on Saturday carried out its first airdrop of aid into the coastal enclave, with a U.S. military transport plane dropping 38,000 meals along Gaza's Mediterranean coastline.

Critics of airdrops say they have only a limited impact on the suffering, and that it is nearly impossible to ensure supplies do not end up in the hands of militants.

The United States will continue these airdrops, Harris said and added that Washington was working on a new route by sea to also send aid.

The war was unleashed in October after Hamas fighters stormed through Israeli towns killing 1,200 people and capturing 253 hostages, according to Israeli tallies. Since then, Israeli forces have killed more than 30,000 Palestinians, according to Gaza health authorities.

Swathes of the Gaza Strip have been laid to waste, nearly the entire population has been made homeless, and the United Nations estimates a quarter of Gazans are on the verge of famine.

At a morgue outside a Rafah hospital on Sunday morning, women wept and wailed beside rows of bodies of the Abu Anza family, 14 of whom Gaza health authorities say were killed in an Israeli airstrike in Rafah overnight.

The youngest of the family who were killed were infant twins Wesam and Naaem, the first children of their mother after 11 years of marriage. They were born a few weeks into the Gaza war.

"My heart is gone," wailed Rania Abu Anza, who also lost her husband in the attack. "I haven't had enough time with them."