US President Joe Biden said on Friday that Israel was offering a new roadmap towards a full ceasefire in Gaza that he urged Hamas to accept, saying it's "time for this war to end."

Biden's intervention, which had been heavily trailed, came as Israeli troops pushed into central Rafah, escalating its nearly eight-month war with Hamas despite international objections to any assault on the south Gaza city.

It also came as top diplomat Antony Blinken acknowledged that despite US efforts to get more aid into Gaza, the humanitarian situation in the Palestinian territory remained "dire."

In his first major address outlining how the Gaza war might end, Biden said that Israel's three-stage offer would begin with a six-week phase that would see Israeli forces withdraw from all populated areas of Gaza.

It would also see the "release of a number of hostages, including women, the elderly, the wounded, in exchange for (the) release of hundreds of Palestinian prisoners."

Israel and the Palestinians would then negotiate during those six weeks for a lasting ceasefire – but the truce would continue while the talks remained underway, Biden said.

The US president urged Hamas to accept the Israeli offer.

"It's time for this war to end, for the day after to begin," he said, adding: "We can't lose this moment" to seize the chance for peace.

After successive rounds of indirect negotiations in recent months all failed, Hamas said earlier on Friday that it had informed mediators it would only agree a "comprehensive" truce including a hostage-prisoner swap if Israel halts its "aggression."

Ismail Haniyeh, the head of Hamas's Qatar-based political office, accused Israel of "using negotiations as a cover to continue its aggression," saying Hamas "refuses to be a part of these manoeuvres."

Israel has repeatedly vowed to destroy Hamas since the Palestinian militant group attacked southern Israel on October 7.

Israel sent tanks and troops into Rafah in early May, ignoring concerns over the safety of displaced Palestinian civilians sheltering in the city on the Egyptian border.

On Friday, soldiers were operating in the city centre where they uncovered rocket launchers and tunnel shafts and dismantled a Hamas weapons storage facility, the army said.

A stream of civilians has flooded out of Rafah, taking their belongings on their shoulders, in cars or on donkey-drawn carts.

Before the Rafah offensive began, the United Nations said up to 1.4 million people were sheltering in the city. Since then, one million have fled the area, the UN agency for Palestinian refugees, UNRWA, has said.

The Israeli seizure of the Rafah crossing has further slowed sporadic deliveries of aid for Gaza's 2.4 million people and effectively shuttered the territory's main exit point.

Israel said at the weekend that aid deliveries had been stepped up.

But US Secretary of State Antony Blinken acknowledged on Friday that the humanitarian situation was "dire" despite US efforts to bring in more assistance.

The World Food Programme said daily life had become "apocalyptic" in parts of southern Gaza since Israel began its assault on Rafah in early May.

The agency was able to provide "ever decreasing amounts of assistance," with all of its bakeries in Rafah closed due to a lack of fuel and supplies, its director for the Palestinian territories, Matthew Hollingworth, said.

Jordan announced it will host a summit on June 11, jointly organised with Egypt and the United Nations, bringing together aid agency chiefs and heads of donor governments to discuss the humanitarian response.

The Gaza war was sparked by Hamas's October 7 attack on southern Israel, which resulted in the deaths of 1,189 people, mostly civilians, according to a tally based on Israeli official figures.

Militants also took 252 hostages, 121 of whom remain in Gaza, including 37 the army says are dead.

Hamas released a video on Telegram on Friday featuring the audio of a woman's voice, who they said was one of the hostages. The audio file could not immediately be verified.

Israel's retaliatory offensive has killed at least 36,284 people in Gaza, mostly civilians, according to the Hamas-run territory's health ministry. (AFP)