This handout picture shows Israeli tanks and soldiers stationed at a location in Gaza Strip. AFP

The United States hailed a "promising start" to Gaza ceasefire talks Thursday, as pressure mounted for a deal to halt the spread of a war that the Hamas-run territory's health ministry said has killed 40,000.

The conflict has devastated Gaza, displaced nearly all of its population at least once and triggered a towering humanitarian crisis.

Talks involving CIA director William Burns opened in the Qatari capital Doha, US National Security Council spokesman John Kirby said.

It was not immediately clear if Hamas had sent any delegates to the meeting, which Israel planned to attend.

"Today is a promising start," Kirby told reporters in Washington, adding: "There remains a lot of work to do." The talks were expected to continue on Friday, he said.

"We need to see the hostages released, relief for Palestinian civilians in Gaza, security for Israel and lower tensions in the region, and we need to see those things as soon as possible," he added.

Mediation efforts have repeatedly stalled since a week-long ceasefire in November — the only pause so far in the war — when dozens of hostages were released by fighters in exchange for Palestinian prisoners held in Israeli jails.

US Secretary of State Antony Blinken speaks during a press conference. File photo

Hamas has rejected Israel's latest demands, which include a lasting military presence along the border with Egypt and a line bisecting Gaza where it would search Palestinians returning to their homes to root out militants. Hamas spokesman Osama Hamdan told The Associated Press the group is only interested in discussing the implementation of Biden's vision and not in further negotiations over its content.

The Hamas official said the movement was "continuing its consultations with the mediators", after demanding the implementation of a proposal that US President Joe Biden laid out on May 31, instead of holding more talks.

The phased plan would start with an initial six-week "complete ceasefire", the release of some hostages held in Gaza and a "surge" in humanitarian aid entering the besieged territory as the warring sides negotiate "a permanent end to hostilities", Biden said at the time.

US Secretary of State Antony Blinken told several Middle Eastern counterparts in recent days that "this ceasefire deal is of vital importance, that we need to do everything we can to get it done, and that escalation is in no one's interest", State Department spokesman Vedant Patel said on Wednesday.

Hamas political official Osama Hamdan speaks during an interview in Doha, Qatar, on Tuesday. AP

The latest mediation push comes as regional tensions have soared following the July 31 killing of Hamas political leader and truce negotiator Ismail Haniyeh during a visit to Tehran.

Iran and its allies blamed Israel, which has not claimed responsibility for the attack that Tehran and armed groups it backs in the region have vowed to avenge, raising fears of a wider conflict more than 10 months into the Israel-Hamas war in Gaza.

'No one knows'

Western leaders have urged Tehran to avoid attacking Israel over Haniyeh's killing, which came hours after an Israeli strike in Beirut killed a senior commander of Hamas ally Hezbollah, the powerful Iran-backed group in Lebanon.

Asked whether a ceasefire agreement in Gaza could stave off a feared Iranian attack on Israel, Biden said: "That's my expectation".

Iranians attend the funeral procession of assassinated Hamas chief, Ismail Haniyeh in Tehran on August 1. Reuters

Iranian foreign ministry spokesman Nasser Kanani said Tehran rejects Western calls "to take no deterrent action against a regime which has violated its sovereignty", referring to Israel.

Last week the Iranian mission to the United Nations expressed "hope" that the retaliation would not be "to the detriment of the potential ceasefire" in Gaza.

A spokesman for Israeli Prime Minister Benjamin Netanyahu told the media that the heads of the Mossad spy agency and Shin Bet secret service would attend the Doha talks.

State Department spokesman Patel earlier told reporters that Qatar was "working to ensure that there is Hamas representation as well".

Qatar's Prime Minister Sheikh Mohammed bin Abdulrahman Al-Thani discussed in a phone call Wednesday with Blinken "joint mediation efforts to end the war" and "the need for de-escalation", the Qatari foreign ministry said.

Both men said "no party in the region should take actions that would undermine efforts to reach a deal," according to a US State Department readout of the call.

Israeli President Isaac Herzog said on social media platform X that the country remained on "high alert" over "the hate-filled threats of the Iranian regime and its terrorist proxies".