CAIRO (AP) - Palestinian factions trying to hammer out a power-sharing agreement are struggling to reconcile their differences toward peace talks with Israel, a Hamas spokesman said Thursday, as the Palestinian president agreed to release dozens of Hamas prisoners in a goodwill gesture during the talks.

Fawzi Barhoum, the militant group’s spokesman, said the disagreement over Israel is one of the key hurdles holding up the formation of a new unity government between Hamas and the more moderate Fatah faction.

Egypt, which is mediating between rival Palestinian factions in the talks that began this week in Cairo, and Palestinian President Mahmoud Abbas’ Fatah have repeatedly said that any new Palestinian government should accept previous peace agreements with Israel and Arabs’ peace overtures to the Jewish state.

That would include recognizing Israel’s right to exist - which Hamas rejects.

"We were not part of these agreements, and therefore, no one should expect us to endorse them," Barhoum told The Associated Press in Cairo.

Instead, Hamas is insisting that the concept of the Palestinians’ right to resistance to Israel be included in the political agenda of any future unity government, said a Fatah official, Ibrahim Aboul Maja.

Another Fatah leader, Azzam al-Ahmed, said Thursday that the groups have been unable to agree on any of the other key issues before them during the three days of talks, but he said the two sides would continue negotiating.

Egypt has set a Saturday deadline for the factions to produce an agreement and hopes to host a signing ceremony by the end of March.