US President Joe Biden called on Hamas on Tuesday to accept a Gaza ceasefire deal by the Muslim holy month of Ramadan, while the Palestinian militant group warned talks for a truce and hostage release cannot go on "indefinitely".

As famine threatens Gazans, US and Jordanian planes again airdropped food aid into the besieged territory of 2.4 million people in a joint operation with Egypt and France.

US Vice President Kamala Harris has expressed "deep concern about the humanitarian conditions in Gaza", while the World Health Organization (WHO) has reported children dying of starvation in two northern Gaza hospitals.

Envoys from Hamas and the United States have been meeting Qatari and Egyptian mediators in Cairo for negotiations over a six-week truce, the exchange of dozens of remaining hostages for hundreds of Palestinian prisoners and the flow of aid to Gaza.

Egypt's Al-Qahera News, which is close to the country's intelligence services, said the talks would continue for a fourth consecutive day on Wednesday.

Biden warned Hamas to agree to a Gaza truce by Ramadan, which begins early next week, after his top diplomat Antony Blinken urged it to accept an "immediate ceasefire".

"It's in the hands of Hamas right now," the US president told reporters from Maryland.

"There's got to be a ceasefire because Ramadan -- if we get into circumstances where this continues to Ramadan, Israel and Jerusalem could be very, very dangerous."

He did not elaborate but the United States urged Israel last week to allow Muslims to worship at the flashpoint Al-Aqsa mosque compound in Jerusalem during Ramadan.

The Israeli government said it would allow Muslim worshippers access to Al-Aqsa during Ramadan "in similar numbers to those in previous years".