Israel Gaza fighting
Smoke billows over Khan Yunis in the southern Gaza Strip during an Israeli bombardment. AFP

US President Joe Biden warned Israel on Thursday that it cannot use aid as a "bargaining chip" in its fight against Hamas and called for an immediate temporary ceasefire in Gaza, where fears of a looming famine have multiplied.

Using his annual State of the Union address to deliver some of his strongest comments yet about the five-month-long war, Biden also ordered the US military to lead "an emergency mission" to build a temporary pier off Gaza to facilitate more aid deliveries.

His address was delivered to Congress as hopes dimmed for a new truce before the start of Ramadan after Hamas negotiators left talks with mediators in Egypt to consult with the movement's leadership in Qatar.

"To the leadership of Israel I say this -- humanitarian assistance cannot be a secondary consideration or a bargaining chip," Biden said.

"Protecting and saving innocent lives has to be a priority."

Biden said the temporary pier, announced before his address, would be able to "receive large ships carrying food, water, medicine and temporary shelters".

Biden, who is facing political pressure over his steadfast support for Israel despite the worsening humanitarian crisis in Gaza, stressed "no US boots will be on the ground" as part of the project.

US personnel would remain offshore while allies manage onshore operations from the port. The plan would also involve a maritime aid corridor from Cyprus.

European Commission president Ursula von der Leyen is expected in the Mediterranean island on Friday for talks on the planned corridor.

The United States, Israel's strongest ally, carried out another airdrop of aid into Gaza on Thursday -- its third in less than a week -- along with aircraft from Jordan, Belgium, Egypt, France and the Netherlands.

"It's easier, it's faster, it's cheaper, particularly if we know that we need to sustain humanitarian assistance to Gazans for a long period of time," the former Dutch finance minister said.

US officials said before Biden's address that it would be a "number of weeks" before aid deliveries to the planned port could begin, but said the administration would not "be waiting on the Israelis".

One official described it as "a moment for American leadership", in a sign of growing White House frustration with Israel's failure to allow more relief into Gaza.

The war in Gaza began after Hamas's unprecedented October 7 attack on southern Israel that resulted in about 1,160 deaths, most of them civilians, according to Israeli figures.

Hamas militants also took around 250 Israeli and foreign hostages, some of whom were released during a week-long truce in November. Israel believes 99 hostages remain alive in Gaza and that 31 have died.

Israel has responded with a relentless bombardment, alongside a ground offensive, that the health ministry in Hamas-run Gaza says has killed 30,800 people, mostly women and children.

The United Nations has warned repeatedly that famine is looming in Gaza, where one of its agencies said the war had damaged around half of all buildings by late January and rendered the territory "uninhabitable" for its 2.4 million people.

In the wasteland of Jabalia in northern Gaza, Palestinians gathered to receive meals at a distribution point.

"There is no gas to cook our food on. There is no flour or rice," said Bassam al-Hou, standing among the rubble.

He said children "are dying and fainting in the streets from hunger".

In Deir al-Balah in central Gaza, around 14 bodies lay in front of a hospital, the bare feet of some protruding from under coloured cloths.

Gaza's health ministry said on Wednesday 20 people had died of malnutrition and dehydration, at least half of them children.

The UN's World Food Programme has warned that without land routes, the volume of aid that could be airdropped would do nothing to avert famine.

Biden had urged Hamas to accept a ceasefire plan with Israel before the Muslim holy fasting month of Ramadan, which could begin as early as Sunday depending on the lunar calendar.

The proposed deal would pause fighting for "at least six weeks", see the "release of sick, wounded, elderly and women hostages", and allow for "a surge of humanitarian assistance", the White House said.

Hamas's delegation voiced dissatisfaction with Israeli responses so far before leaving Cairo, although US ambassador to Israel Jack Lew denied the talks had "broken down".

"The differences are being narrowed... Everyone's looking towards Ramadan, which is coming close. I can't tell you that it will be successful, but it is not yet the case that it is broken down," Lew said.

Israeli war cabinet member Gadi Eisenkot said Hamas was under "very serious pressure" from mediators to make a "counter-offer".

"Then it will be possible to advance it and take a position," he said.

In the grey ruins of Khan Yunis, southern Gaza's largest city, dozens of people went to inspect their homes after Israeli forces pulled out of the city centre, an AFP correspondent said.

The army has yet to respond to an AFP request to confirm a withdrawal from the area.

Israeli Prime Minister Benjamin Netanyahu has faced increasing public pressure over the fate of hostages still held and from anti-government protests.

He has vowed to press on with the campaign to destroy Hamas, before or after any truce deal.