DAMASCUS, Syria - A senior Hamas official in Syria on Saturday announced that his group was boycotting this weekend's Palestinian reconciliation talks with rival Fatah.

The talks were to start in Cairo, Egypt, on Sunday. The two feuding sides were expected to discuss forming a joint government, rebuilding security forces and setting a date for presidential and legislative elections.

But deputy Hamas leader Moussa Abu Marzouk told The Associated Press that Fatah had reneged on a pledge to release Hamas prisoners it holds ahead of the dialogue, prompting the boycott. He acknowledged that many issues had been settled but that the prisoners issue was too important to disregard.

Abu Marzouk blamed Palestinian leader Mahmoud Abbas for the talks' collapse.

"Going there (to the talks) is not a target in itself. The target is to reunite Palestinian groups," Abou Marzouk said. He also said Egypt's "vision" for reconciliation "does not represent the Hamas point of view." He did not elaborate.

The Fatah delegation, already in the Egyptian capital on the eve of the talks, expressed shock at Hamas' decision.

"This decision is unwise ... it shows that Hamas doesn't want a solution. I think that the consequences will be very dangerous," said Ahmed Abdel Rahman, a member of the Fatah team in Cairo. "We are shocked by this decision. It shows that Hamas is irresponsible when it comes to the fate of the Palestinian people."

Abbas' spokesman Nabil Abu Rdeineh said Hamas' pretext for staying away was "unacceptable."

Hamas reportedly wants the release of some 500 Palestinians it says Fatah is holding in its jails.

In the West Bank town of Jenin, Palestinian Prime Minister Salam Fayyad, who is in charge of security forces, said that Fatah has no political prisoners and holds only "detainees for breaking the law."

Hamas' "hesitation and stalling don't serve the goal of reuniting the homeland," added Fayyad, who spoke during a joint press conference with visiting U.S. Secretary of State Condoleezza Rice.

Egyptian Foreign Ministry spokesman Hossam Zaki confirmed to the AP that the talks had been canceled because of the Hamas boycott and said a statement would be issued soon.

An Egyptian security official said Egypt turned back at the Rafah border crossing with the Hamas-controlled Gaza Strip some 35 representatives of various Palestinian factions who were about to enter Egypt to take part in the talks after they had been canceled. The official spoke on condition of anonymity because he was not authorized to speak to the press.

Damascus-based Hamas leader Khaled Mashaal had said last week that his group was "eager" for national reconciliation and voiced support for the Cairo talks. But he also told reporters during a visit to Beirut that there were still "obstacles."

Several rounds of power-sharing talks have failed since Hamas won parliament elections in 2006.

Fatah and Hamas have been at odds since the Hamas' violent takeover of the Gaza Strip in June 2007. Following the takeover, Abbas dissolved the Hamas-led government from his base in the West Bank and formed a new administration excluding the more radical group.

Officials of other Damascus-based groups including Islamic Jihad and the Popular Front for the Liberation of Palestine-General Command said they would also stay away from the talks.

Anwar Raja of the PFLP-FC said the Egyptian sponsors were biased.