The war between Israel and Hamas entered its seventh month on Sunday as US and other negotiators were expected to join the protagonists in Cairo in a renewed push for a ceasefire and hostage release deal.

Egypt's Al-Qahera News said CIA Director Bill Burns and Qatari Prime Minister Sheikh Mohammed bin Abdulrahman bin Jassim Al-Thani would join Egyptian mediators for Sunday's indirect talks between the Israeli and Hamas delegations.

Hamas confirmed ahead of the talks that its core demands were a complete ceasefire in Gaza and the withdrawal of Israeli forces.

The ceasefire attempt comes after Israel's military made a rare admission of wrongdoing and said it was firing two officers over the killing of seven aid workers in Gaza, where humanitarians say famine is imminent.

The admission over the deaths of the workers from US-based World Central Kitchen (WCK) on April 1 did not quell calls for an independent probe.

"It's been six months of targeting anything it seems moves," Spanish-American celebrity chef and WCK founder Jose Andres told ABC News.

"This really at this point seems it's a war against humanity itself."

The deaths of the aid workers led to a tense call between US President Joe Biden and Israel's Prime Minister Benjamin Netanyahu.

Biden urged an "immediate ceasefire" and for the first time hinted at making US support for Israel conditional on curtailing the killing of civilians and improving humanitarian conditions.

The bloodiest-ever Gaza war began on October 7 with an unprecedented attack from Gaza by Hamas militants resulting in the death of 1,170 people, mostly civilians, Israeli figures show.

Palestinian militants also took around 250 Israeli and foreign hostages, about 130 of whom remain in Gaza, including more than 30 the military says are dead.

The Israeli military announced on Sunday another four of its troops had been killed in Gaza, bringing the toll to 260 since the beginning of ground operations in late October.

President Isaac Herzog, whose post is largely ceremonial, said Israel was approaching the half-year mark in a "bloody and difficult war" that began with "the cruel terror attack and the horrific massacre".

- 'Empty shell' -

Israel's retaliatory offensive against Hamas has killed at least 33,137 people in Gaza, mostly women and children, according to the health ministry in the Hamas-run territory.

A World Health Organization-led mission finally gained access to Gaza's largest hospital, Al-Shifa, which was reduced to ashes by a two-week Israeli raid.

WHO chief Tedros Adhanom Ghebreyesus said the Gaza City hospital was "now an empty shell with human graves".

He said the team had seen "at least five dead bodies during the mission".

Biden wrote to the leaders of Egypt and Qatar ahead of Sunday's talks urging them to secure commitments from Hamas to "agree to and abide by a deal", a senior administration official told AFP.

Stop-start talks have made no headway since a week-long truce in November saw some hostages exchanged for Palestinian prisoners detained by Israel.

Biden's Thursday call with Netanyahu included discussions on "empowering his negotiators" to reach a deal, National Security Council spokesman John Kirby said.

Washington blames the lack of a deal on Hamas's refusal to release sick and other vulnerable hostages. Qatar has said Israeli objections to the return of displaced Gazans are the main obstacle.

Biden is under pressure over massive US military aid to Israel which Washington so far has not leveraged despite increasingly critical comments about Israel's conduct of the war.

Israel's opposition chief Yair Lapid headed to Washington Saturday for talks with top officials, his centrist Yesh Atid party said.

Lapid is expected to meet Secretary of State Antony Blinken and National Security Advisor Jake Sullivan, amid deepening frustration with Netanyahu.

He will also meet Senate Majority Leader Chuck Schumer, who last month called for a snap Israeli election to give voters a chance to get rid of Netanyahu.

Ten of thousands of Israelis, including Lapid, protested against Netanyahu in Tel Aviv and other cities Saturday, demanding "elections now".

- 'Criminal' -

British Prime Minister Rishi Sunak said on Saturday "this terrible conflict must end".

"We continue to stand by Israel's right to defeat the threat from Hamas terrorists and defend their security. But the whole of the UK is shocked by the bloodshed," he said in a statement.

The Israeli military announced it was firing two officers after finding a series of errors led to the drone strikes that killed the WCK workers.

It said a commander "mistakenly assumed" Hamas had seized the aid vehicles, which were moving at night.

Australia has criticised Israel's response to the deaths of the aid workers, who included Australian Lalzawmi "Zomi" Frankcom, and has said it will appoint a special adviser to work with Israel to ensure "transparency" in its investigation.

WCK's Gaza operations remain suspended after the attack, while other global aid groups said relief work in the territory has become almost impossible.

Israel announced hours after Biden and Netanyahu spoke that it would allow "temporary" aid deliveries through Ashdod port and the Erez border crossing.

UN chief Antonio Guterres called for a "paradigm shift" rather than "scattered measures".

Mahmud Bassal, spokesman for Gaza's Civil Defence agency, told AFP on Saturday that aid reaching Gaza is "absolutely not sufficient" for its 2.4 million people.

Around 1.5 million Gazans are sheltering in Rafah in the territory's far south near the border with Egypt.

"We are ordinary citizens and human beings," Siham Achur, 50, said in the tent that is now her family's home. "Why did they bomb our house?"