A long-awaited ceasefire in the Israel-Hamas war was delayed on Sunday after Prime Minister Benjamin Netanyahu said at the last minute that it would not take effect until the Palestinian militant group provided a list of the hostages to be released.

Hamas, while "affirming its commitment" to the terms of the ceasefire, said: "The delay in providing the names of those to be released in the first batch is due to technical reasons."

A statement from Netanyahu's office, issued less than an hour before the truce was to start, said he had "instructed the IDF (military) that the ceasefire... will not begin until Israel has received the list".

The initial exchange was to see three Israeli hostages released from captivity in return for a first group of Palestinian prisoners.

If the ceasefire goes ahead, a total of 33 hostages taken by militants during Hamas's October 7, 2023 attack on Israel will be returned from Gaza during an initial 42-day truce.

Under the deal, hundreds of Palestinian prisoners will be released from Israeli jails.

The truce is intended to pave the way for an end to more than 15 months of war sparked by the October 7 attack, the deadliest in Israeli history.

It follows a deal struck by mediators Qatar, the United States and Egypt after months of negotiations, and takes effect on the eve of Donald Trump's inauguration as US president.

In a televised address on Saturday, Prime Minister Benjamin Netanyahu said Israel had US support to return to war if necessary.

Calling the 42-day first phase a "temporary ceasefire", he said: "If we are forced to resume the war, we will do so with force."

Fighting continued right up to the eve of the truce, with Gaza's civil defence agency saying that at least five members of one family were killed when an Israeli strike hit their tent in the southern city of Khan Yunis. (AFP)