The Palestinian militant group Hamas said on Tuesday it had delivered its response to a proposed ceasefire deal for Gaza, and the United States said it believed an agreement was possible.

Details of Hamas' response were not immediately revealed but Qatar, which helped mediate the proposal that was passed on to Hamas last week and would also involve the release of hostages held in Gaza, said the reply had made Doha "optimistic".

US Secretary of State Antony Blinken, on a lightning tour of the Middle East, said Washington was reviewing Hamas' response and that he would discuss it with Israeli officials when he visits the country on Wednesday.

"There’s still a lot of work to do be done, but we continue to believe that an agreement is possible, and indeed essential," he told a press conference in Doha with Qatari Prime Minister and Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani.

Qatari Prime Minister and Foreign Minister Sheikh Mohammed Bin Abdulrahman Bin Jassim Al Thani speaks during a joint press conference with Turkish Foreign Minister Hakan Fidan, in Doha, Qatar Oct 25, 2023. |REUTERS/Imad Creidi

After Hamas issued a statement saying it had submitted its response to the ceasefire proposal, Sheikh Mohammed said it had been a "positive response" but declined to give further details.

The proposed deal, drawn up more than a week ago by US and Israeli spy chiefs at a meeting with the Egyptians and Qataris, would secure the release of remaining hostages held by militants in Gaza in return for a long pause to fighting.

Hamas has said previously that any deal must bring about a definitive end to the war. Israel has said it will not halt the war permanently until Hamas is destroyed.

Sources close to the talks have said the truce would last at least 40 days, during which militants would free civilians among remaining hostages they hold. Further phases would follow, to hand over soldiers and dead bodies of hostages, in exchange for releases of Palestinians imprisoned in Israel.

The only truce so far, in November, was initially agreed for just four days and extended to last a week. At the time, Hamas released 110 hostages in exchange for 240 Palestinian prisoners in Israeli jails.

Israel began its military offensive in Gaza after militants from Hamas-ruled Gaza killed 1,200 people and took 253 hostages in southern Israel on Oct 7.

Gaza's Health Ministry says at least 27,585 Palestinians have been confirmed killed in Israel's military campaign, with thousands more feared buried under rubble.