Hamas will respond to an Israeli truce proposal for Gaza "within a very short period", an official with the Palestinian militant group said Wednesday, stressing though that any ceasefire needs to be permanent.

Hamas is considering a plan for a 40-day ceasefire and the exchange of scores of hostages for larger numbers of Palestinian prisoners.

Suhail al-Hindi, a senior Hamas official, told AFP the group would "deliver its response clearly within a very short period", although he would not say precisely when that was expected to happen.

Speaking to AFP by phone from an undisclosed location, he said it was premature to say whether the Hamas envoys, who have returned from talks in Cairo to their base in Qatar, felt any progress was made.

He stressed the aim was "to reach an end to this war".

But that would seem to be at odds with Israel's determination to push ahead with its vast ground offensive in southern Gaza.

A source with knowledge of the negotiations said Qatari mediators expected a response from Hamas in one or two days.

The source said Israel's proposal contained "real concessions" including a period of "sustainable calm" following an initial pause in fighting and the exchange of hostages of and prisoners.

The source said Israel's withdrawal from the Gaza Strip remained a likely point of contention.

An Israeli official told AFP the government "will wait for answers until Wednesday night", and then "make a decision" whether to send envoys to Cairo to nail down a deal.