A senior Hamas official said on Wednesday there had been progress in negotiations to end the Gaza conflict but the Islamist militants needed detailed guarantees that Israel would ease its blockade of the enclave.
Talks to end the 16-day conflict have intensified with US Secretary of State John Kerry shuttling between Jerusalem and Cairo in a bid to forge a truce.
Hamas, which sparked the conflict by firing rockets from Gaza into Israel, had rejected an Egyptian proposal that called for a ceasefire first and then negotiations.
The Hamas official acknowledged that the militants realised that getting Israel to end the eight-year siege in tandem with a ceasefire was unrealistic.
"There needs to be an agreement on the principles, the schedule (for ending the blockade) and the mechanism," the official said.
Hamas's chief Khaled Meshaal on Wednesday again insisted on a ceasefire only after an end to the siege, in force since militants kidnapped an Israeli soldier in 2006.
The official, who works closely with Meshaal, said however that they understood that the blockade would be eased only after the ceasefire, but they required a schedule in place first.
The conflict has killed 659 Palestinians, 34 Israelis and a Thai worker in Israel, which had accepted the Egyptian truce last week.
The official said he hoped the negotiations would bear fruit "in a few days."
"The atmosphere in the talks is positive," he told AFP in a telephone interview.
Kerry had also said negotiations were making progress. "But there is still work to be done," he told reporters in Jerusalem.
Hamas is blacklisted by Israel and the United States as a terrorist organisation and conducts the negotiations through intermediaries.
It violently seized complete control of the coastal strip in 2007 after winning an election, and has fought three conflicts with Israel since.
Aides travelling with Kerry voiced hope that the diplomat could find a way for Israel and Hamas to end the violence and then negotiate indirectly.
"There are a number of different ideas out there for how the ceasefire could work - there are a number of different formulas - and we're open to any of them," a senior US official said after Kerry met Israel's Prime Minister Benjamin Netanyahu.
-'Talk of guarantees'-
The Hamas official said the Islamists required firm guarantees and details before signing off an a truce.
"There should be guarantees by the parties demanding a ceasefire," he added, referring to the United States but also to Egypt, which controls the Rafah border crossing with Gaza.
The official asked to remain anonymous because he was not authorised to share details of the negotiations.
Egypt brokered a truce in 2012. But its new President Abdel Fattah al-Sisi, who overthrew the Islamist government last year, has been hostile to Hamas and commands less influence over the militants across the border.
Meshaal, who is based in the Qatari capital Doha, said in a press conference that Washington had offered to "guarantee" such an agreement, but it had a track record of not following through.
Another Hamas official, Osama Hamdan, said Kerry's commitments were vague.
"There are no American guarantees," he said in an interview with the Qatari-owned Al-Jazeera broadcaster.
"There is talk that guarantees will come," he said, adding that Hamas required clarifications.
Hamas's position has been bolstered by support from Palestinian president Mahmud Abbas, an opponent of the Islamists before agreeing a unity deal with them in April.
Abbas's PLO has said it agreed with Hamas's demands, which also include freeing Palestinian prisoners. He met Kerry in Ramallah on Thursday.