Rudwan al-Akhras, the Fatah representative in the dialogue, said on Wednesday - the fourth day of inconclusive coalition talks in Gaza - that the gap with Hamas's position was still big.
Aljazeera reported him as saying that all the presentations and amendments in the revised Hamas offer did not meet the minimum demands of Fatah for joining a Hamas-led government.
Reuters quoted Akhras as saying: "I do not see any encouraging signals that we will be able to reach an agreement over the programme to form a joint government between the factions."
Salah al-Bardaweel, the Hamas parliamentary bloc spokesman, was quoted by Aljazeera as saying that the Islamist group took note of the remarks made by other blocs on the revised programme and would study them carefully before putting forth a fresh offer to serve as the basis for more talks.
The dialogue would end by the weekend and then Hamas would announce its government, Aljazeera reported, quoting Bardaweel.
Palestinian officials said Fatah and Hamas were trying to find common ground and avoid tensions that could result in political paralysis or even violence, but that a confrontation was inevitable.
Palestinian officials involved in the talks said the main sticking points were Hamas's refusal to accept existing agreements and respect obligations by the Palestine Liberation Organisation, which includes recognition of Israel.
Hamas wants other factions to
participate in the government
Hamas, whose charter calls for Israel's destruction, swept to victory over the long-dominant Fatah faction in an election in January on pledges to clean up corruption in the Palestinian Authority and seek statehood through armed struggle.
Earlier on Wednesday, the Fatah movement of Mahmoud Abbas, the Palestinian president, cast doubt on the chances of a deal. The leaders are expected to reconvene on Thursday.
In addition to what Bardaweel said would be Hamas's final offer, the group has revised its government programme twice this week after being rebuffed by Fatah.
He said: "I do not think that more discussion will change the programme."
"Hamas has made a lot of progress towards a middle ground."
But he said that Fatah cannot expect Hamas to drop its own programme and adopt Fatah's. "This contradicts the will of the people."
Abbas has given Hamas two weeks to clarify its position before it presents an administration to parliament for a confidence vote.
Wolfensohn says his mandate
and backing are unclear
Elsewhere, the envoy for the Quartet group of international mediators in the Israeli-Palestinian conflict, James Wolfensohn, threatened to quit on Wednesday because his mandate and backing were unclear after Hamas's electoral victory.
The former World Bank head had been charged by the Quartet - the US, EU, Russia and the UN - with raising funds for Palestinians after Israel withdrew from Gaza last year.
"The Quartet itself must continue, but the role of a disenfranchised leader of that Quartet does not seem to me to be a particularly attractive thing to spend your life doing," Wolfensohn said at a US congressional hearing.