by Steve Weizman

RAMALLAH, Palestinian Territories (AFP) – A surprise deal to end decades of rivalry between Fatah and Hamas was welcomed by the Palestinian leadership on Thursday, but denounced by Israel as crossing "a red line."
The agreement, announced in Cairo on Wednesday, saw the secular Fatah party which dominates the West Bank-based Palestinian Authority and Gaza's Islamist rulers agree to form a transitional government ahead of elections, within a year.
The announcement provoked a chorus of condemnation from the Israeli leadership, who said it would harm chances for peace, but Hamas said it had no plans to stop Fatah from holding negotiations without its participation.
Top Hamas and Fatah officials involved in the Cairo talks said the breakthrough had come about as a result of both the impasse in peace negotiations with Israel and the ongoing upheaval in the Arab world.
Senior Hamas official Mahmud Zahar pointed to "a change in the (regional) political environment, and the failure in negotiations," while Azzam al-Ahmed, who headed the Fatah delegation, agreed the Arab Spring "put pressure" on both factions.
Wednesday's deal, which came after 18 months of fruitless talks, will see the two parties work together to form an interim government of independent politicians chosen by both sides, Ahmed said.
"This government will be tasked with preparing for presidential and legislative elections within a year," he told AFP by phone from Cairo.
Hamas officials said the parties would return to Cairo on Wednesday to sign the document, which also lays out terms for the release of political detainees by both sides.
Zahar also said the two factions had settled their differences on security, a key issue which has bedevilled the past 18 months of negotiations.
And Mussa Abu Marzuk, a top member of Hamas's exiled leadership in Damascus, told reporters consultations on the interim government would begin after next week's signing ceremony.
The European Union and United Nations issued cautious statements on the deal.
EU foreign policy chief Catherine Ashton said she was following the situation "with great interest," while the UN's Middle East peace envoy Robert Serry said the UN "strongly supports all efforts for progress towards reunification of Gaza and the West Bank."
But Israel lashed out at the deal, with top officials warning that an alliance between Fatah and the Islamists would damage chances for a peace deal.
"With this accord, a red line has been crossed," Israel's ultra-nationalist Foreign Minister Avigdor Lieberman told military radio, while Defence Minister Ehud Barak vowed Israel would "never negotiate with Hamas."
Even doveish Israeli President Shimon Peres slammed the move, saying Abbas risks being tainted if he embraces Hamas.
"I call upon my friends in the leadership of Fatah: unite for peace, don't make compromises, don't permit a division that legitimises destruction and hatred," he said.
But Abbas, speaking in Ramallah, said the interim government would not dictate policy when it came to negotiations, which would remain the mandate of the Palestine Liberation Organisation he heads.
"This government is authorised to do two things: fix a date for the elections and rebuild Gaza. Politics is for the PLO and we will continue to follow my policies," he said at a press conference after meeting Israeli peace activists.
Israel's Benjamin Netanyahu on Wednesday issued an Abbas with an ultimatum.
"Choose between peace with Israel or peace with Hamas. There cannot be peace with both because Hamas strives to destroy the state of Israel and says so openly," said the prime minister.
Hamas's Zahar said the Islamists had no plans to talk with Israel but would not stop Abbas and Fatah from doing so.
"If Fatah wants to bear the responsibility for negotiating on nonsense, let it," he told AFP in Cairo. "If it manages to get a state, good for them."
The reconciliation document was first hammered out by Egyptian mediators in October 2009. Fatah signed it, but Hamas negotiators stalled for time over reservations which were never clearly laid out.
Wednesday's deal was based on the same six-point Egyptian document along with an agreement known as the Damascus Understandings, and several other accords, officials said.
Tensions between the two movements date back to the start of limited Palestinian self-rule in the early 1990s. They worsened dramatically in 2007 when Hamas forces ousted Fatah from Gaza after a week of deadly clashes, cleaving the Palestinian territories into hostile rival camps.