The entire population of Gaza is experiencing "severe levels of acute food insecurity", US Secretary of State Antony Blinken said Tuesday, underscoring the urgency for increasing the delivery of humanitarian aid into the Palestinian territory.

"According to the most respected measure of these things, 100 percent of the population in Gaza is at severe levels of acute food insecurity. That's the first time an entire population has been so classified," Blinken told a press conference in the Philippines where he is on an official visit.

Blinken's remarks came on the eve of his return to the Middle East, this time to Saudi Arabia and Egypt, to discuss efforts to secure a ceasefire in Gaza and ramp up aid deliveries.

A United Nations-backed food security assessment warned Monday that half of Gazans are experiencing "catastrophic" hunger, with famine projected to hit the north of the territory by May unless there is urgent intervention.

Martin Griffiths, the UN's humanitarian chief, has called for Israel to allow unfettered aid into the besieged Palestinian territory, saying there was "no time to lose".

The bloodiest-ever Gaza war broke out after Hamas launched an unprecedented attack on Israel on October 7.

Israel responded with a relentless bombing campaign and ground offensive in the Hamas-run Palestinian territory.

With aid agencies reporting huge difficulties gaining access to Gaza, particularly the north, the UN has warned for weeks that a famine is looming.

Donors have turned to deliveries by air or sea, but these are not viable alternatives to land deliveries, UN agencies say.

The Integrated Food Security Phase Classification partnership said Monday that while the technical criteria for a famine had not yet been met, "all evidence points towards a major acceleration of deaths and malnutrition".

Citing UN data, Blinken said 100 percent of the population in Gaza needed humanitarian assistance, compared with 80 percent in Sudan and 70 percent in Afghanistan.

"This only underscores both the urgency, the imperative, of making this the priority," Blinken said of aid deliveries.

"We need more, we need it to be sustained, and we need it to be a priority if we're going to effectively address the needs of people."

Blinken is in Manila as part of a brief Asia tour aimed at reinforcing US support for regional allies against China.

During a joint press conference with his Philippine counterpart, Blinken was asked about steps he was taking to address the lack of access to Gaza for foreign journalists.

"There are obviously profound security considerations in an active war zone and those have to be taken into account," Blinken said.

"But the basic principle of access for journalists is something we stand strongly behind."