Talks on a ceasefire and hostage release deal in the Gaza Strip have resumed in Qatar, as the number of Palestinians reported killed in the war between Israel and Hamas surpassed 40,000.

An agreement is seen as key to stopping the 10-month conflict spiralling into an all-out regional war involving Iran, but expectations of a breakthrough are low.

Hamas has said it will not participate in the indirect negotiations in Doha for now, although mediators are expected to relay messages to the armed group’s officials based there.

It has called for a roadmap based on a proposal outlined by the US president and has accused Israel’s prime minister of adding new conditions, which he has denied.

Israeli media report that the country’s negotiating team has been given a slightly expanded mandate and cited officials as warning that they consider this the “last chance” to get a deal.

Mediators from the US, Qatar and Egypt face a number of potential sticking points, including control of land along Gaza’s border with Egypt and the return of displaced Palestinian civilians to northern Gaza.

The talks have been suspended since Hamas’s political leader and chief negotiator, Ismail Haniyeh, was assassinated in Tehran at the end of July. Iran has vowed to retaliate against Israel, which has neither confirmed nor denied involvement, raising fears of a wider escalation.

The Israeli military launched a campaign in Gaza to destroy Hamas in response to an unprecedented attack on southern Israel on 7 October, during which about 1,200 people were killed and 251 others were taken hostage.

Gaza’s Hamas-run health ministry said on Thursday that at least 40,005 people had been killed in the territory since then, including 40 over the previous 24 hours.

The figure, which does not make a distinction between combatants and civilians, is often disputed by the Israeli government but is broadly accepted by UN agencies.

The Israeli military has told the BBC that more than 15,000 terrorists have been killed. It has also reported that 330 of its troops have been killed since the ground invasion began.

Israel’s delegation to the Doha talks reportedly includes the directors of its Mossad foreign intelligence agency and Shin Bet domestic security service, David Barnier and Ronen Bar, as well as the Israeli military’s hostages chief, Nitzan Alon.

CIA director William Burns is also due to attend, along with Qatari Prime Minister Mohammed bin Abdul Rahman Al Thani and Egyptian intelligence chief Abbas Kamel.

Last week, the mediators called on Israel and Hamas to resume urgent discussions on a deal that would bring relief to the 2.3 million Palestinians in Gaza, as well as the 111 Israeli and foreign hostages still held there, 39 of whom are presumed dead.

A framework agreement was “now on the table with only the details of implementation left to conclude”, they said, adding that they were prepared to present a bridging proposal that overcame their differences if necessary.

The first phase of the deal outlined by US President Joe Biden would include a “full and complete ceasefire” lasting six weeks, the withdrawal of Israeli forces from all populated areas of Gaza, and the exchange of some of the hostages – including women, the elderly and the sick or wounded – for Palestinian prisoners held in Israel.

The second phase would involve the release of all other living hostages and a “permanent end to hostilities”. The third would see the start of a major reconstruction plan for Gaza and the return of dead hostages’ remains.

A senior official in Hamas – which is proscribed as a terrorist organisation by Israel, the UK and other countries – told the BBC on Wednesday that it would not attend the meeting, even though its political leadership is almost entirely based in Doha.

Hamas’s position was that it would “not engage in negotiations for the sake of negotiations in order to provide cover for Israel to continue its war”, the official said.

He claimed that Israel had “added new conditions and reneged on its previous agreement”, including demanding that it maintain full control over the Philadelphi corridor, a narrow strip of land running along Gaza’s southern border with Egypt, and that displaced people returning to northern Gaza be screened to ensure they are unarmed civilians.

Israeli Prime Minister Benjamin Netanyahu’s office issued a statement on Tuesday saying the claim that he had added new conditions was “false”, describing them instead as “essential clarifications to help implement” the initial proposal.

In addition to halting a devastating war and freeing hostages, the US and others see a ceasefire deal as a way to deter Iran from retaliating against Israel for the killing of Ismail Haniyeh, who has been succeeded by Hamas leader in Gaza, Yahya Sinwar, one of the masterminds of the 7 October attack.

The Iran-backed Lebanese Hezbollah movement has also vowed to respond to the killing of a senior commander in an Israeli air strike in Beirut. The Israeli military blamed the latter for a rocket attack that killed 12 children in the Israeli-occupied Golan Heights.

Israel has warned Iran that it would “exact a heavy price for any aggression”, while Iran has insisted “a punitive response to an aggressor is a legal right”.