Hamas submitted its formal response on Tuesday to a proposal outlined by United States President Joe Biden on May 31.
Israel said the response was tantamount to a rejection, while a Hamas official said the Palestinian group merely reiterated long-standing demands not met by the current plan.
Egypt and Qatar said they had received Hamas' response but did not disclose the contents.
Early on Wednesday, Izzat al-Rishq, a member of Hamas' political bureau, said in a statement the group's answer was "responsible, serious and positive" and "opens up a wide pathway" for an accord.
Another Hamas official, who declined to be identified, told Reuters on Tuesday the response reaffirmed the movement's stance that a ceasefire must lead to a permanent end to hostilities in Gaza, withdrawal of Israeli forces, reconstruction of the Palestinian enclave and release of Palestinian prisoners in Israel.
"We reiterated our previous stance. I believe there are no big gaps. The ball is now in the Israeli courtyard," the official said.
The US has said Israel accepted its proposal, but Israel has not publicly stated this.
As Israel has continued assaults in central and southern Gaza that are among the bloodiest of the war, Prime Minister Benjamin Netanyahu has repeatedly said Israel would not commit to an end of its campaign in Gaza before Hamas is eliminated.
An Israeli official said on Tuesday the country had received Hamas' answer via the mediators and that Hamas "changed all of the main and most meaningful parameters."
The Israeli official, who spoke on condition of anonymity, said Hamas "has rejected the proposal for a hostage release that was presented by President Biden."
Earlier a non-Israeli official briefed on the matter, who declined to be identified, said Hamas proposed a new timeline for a permanent ceasefire with Israel and withdrawal of Israeli troops from Gaza, including Rafah.
The United Nations Security Council on Monday voted in favour of a US resolution supporting the proposal outlined by Biden. Hamas official Sami Abu Zuhri told Reuters on Tuesday that it accepted the Security Council resolution and was ready to negotiate over the details of a ceasefire.
US Secretary of State Antony Blinken, in Tel Aviv to meet Israeli officials on Tuesday, described the comments by Hamas as a "hopeful sign" but said they were not conclusive.
More important "is the word coming from Gaza and from the Hamas leadership in Gaza. That’s what counts, and that’s what we don’t have yet," Blinken told reporters in Tel Aviv.
CEASEFIRE PLAN
Biden's proposal envisages a ceasefire and phased release of Israeli hostages in Gaza in exchange for Palestinians jailed in Israel, ultimately leading to a permanent end to the war.
This would be a three-phase plan starting with an initial six-week ceasefire with an Israeli military withdrawal from populated areas of Gaza and the release of some hostages while "a permanent end to hostilities" is negotiated through mediators.
The White House did not immediately respond to a request for comment on the Israeli official’s remarks on Tuesday. Earlier US officials said they were reviewing Hamas’ response, as did Qatar and Egypt.
For months, negotiators from the US, Egypt and Qatar have been trying to mediate a ceasefire in the enclave of 2.3 million people.
Separately, UN Secretary-General Antonio Guterres on Tuesday said in a report to the Security Council that Israel's army and security forces as well as Palestinian militants Hamas and Islamic Jihad killed and maimed children in 2023.
Israel is retaliating against Hamas, which rules Gaza, over a deadly attack by its militants on October 7 last year. More than 1200 people in Israel were killed.
Gunmen took around 250 hostages back to Gaza after the attack and more than 100 were released in exchange for about 240 Palestinians held in Israeli jails in November. There are 116 hostages left in Gaza, according to Israeli tallies, including at least 40 whom Israeli authorities have declared dead in absentia.
Israel launched an air, ground and sea assault on the Palestinian territory, killing more than 37,000 Palestinians, according to Gaza health authorities.
Gaza is now in the grip of a humanitarian crisis due to widespread hunger, scarcity of essentials, infrastructure destruction and continuing displacement of civilians.
The US military resumed bringing humanitarian aid into the enclave via a floating pier on Tuesday after a two-day halt due to bad weather, three US officials said.
The pier was out of operation for 10 days for repairs, and briefly re-opened on Saturday. The UN still is not moving aid from the pier to warehouses while it reviews security.
Call for swift release of Russians
Russia's Human Rights Commissioner says she has issued a fresh appeal to senior UN and other officials to take action to secure the release of Russian nationals still held by Hamas in the Gaza Strip.
Tatyana Moskalkova, writing on the Telegram messaging app, said she had launched the appeal after meeting in Moscow with relatives of those still being held.
"In one conversation, one of the mothers told me details of the situation of those being held," she wrote.
News reports have put at eight the number of hostages holding Russian passports, including three who were released.
Moskalkova said she had appealed to the UN High Commissioner For Human Rights, Volker Turk, the head of the International Committee of the Red Cross, Mirjana Spoljaric, and other officials "for the rapid return home of our compatriots".
Russia has sought to speak to both sides in the conflict in Gaza and a Hamas delegation visited Moscow last year. But President Vladimir Putin has said the violence in the region exposed the failure of US policy, particularly in considering the needs of the Palestinians.
