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Carolyn Kaster, Pool, Associated Press
U.S. Secretary of State John Kerry arrives at Cairo International Airport Sunday, Oct. 12, 2014, to attend a reconstruction conference for Gaza.

CAIRO — Palestinian President Mahmoud Abbas on Sunday promised transparent and responsible use of funds pledged at a donor's conference to help Gaza rebuild after this summer's devastating war between Israel and Hamas.

Speaking at the one-day gathering in Cairo, Western-backed Abbas said $4 billion was needed to reconstruct the coastal strip after the 50-day war that ended on Aug. 27. Participants were expected to pledge hundreds of millions of dollars, and U.S. Secretary of State John Kerry announced immediate U.S. assistance of $212 million as the conference began.

Abbas said the latest Gaza war caused "tragedies that are difficult to be described by words ... Entire neighborhoods have been reduced to rubble and 90 families are no longer listed in the civil register."

"The (Palestinian) government will carry out the reconstruction plan with full responsibility and transparency in coordination with the U.N., the donors, international financial institutions, civil society and the private sector," he said.

Donors plan to funnel the aid through Abbas' Palestinian Authority, and bypass Hamas. On hand for the conference were representatives of more than 50 countries and at least 20 regional and international organizations, including U.N. Secretary-General Ban Ki-moon and European Union negotiator Catherine Ashton.

Leading participants said the reconstruction of Gaza cannot be carried out in isolation from efforts to revive Israeli-Palestinian talks in search of a comprehensive and lasting settlement.

"We must not lose sight of the root causes of the recent hostilities: A restrictive occupation that has lasted almost half a century, the continued denial of Palestinian rights and the lack of tangible progress in peace negotiations," Ban said.

"I call on all parties to come together to chart a clear course toward a just and final peace," he told the conference, held amid tight security at a luxury hotel on the eastern outskirts of Cairo. "Going back to the status quo is not an option; this is the moment for transformational change."

The latest conflict in Gaza was the most ruinous of three wars between Hamas and Israel since 2008, leaving more than 2,000 Palestinians — mostly civilians — killed. Another 11,000 were wounded, and some 100,000 people remain homeless.

Kerry said Gazans "need our help desperately — not tomorrow, not next week, but they need it now." He said the new U.S. money, which nearly doubles American aid to the Palestinians this year, would go to security, economic development, food and medicine, shelter and water and sanitation projects.

Abbas and the militant Hamas group, which has ruled Gaza since 2007, recently formed a national unity government which held its first Cabinet meeting in Gaza last week. But a blockade of Gaza enforced by both Egypt and Israel remains in force, causing the territory of 1.8 million people economic hardships and high unemployment.

Egyptian President Abdel-Fattah el-Sissi, whose government negotiated the cease-fire that ended the war, said the reconstruction effort hinged on a "permanent calm" between Hamas and Israel, and required the exercise of "full authority" by the Palestinian Authority led by Abbas.

Egypt has had tense relations with Gaza's Hamas rulers since the Egyptian military ousted Islamist President Mohammed Morsi in July last year and threw its weight behind the administration of Abbas in the West Bank. Egypt and Israel have enforced a blockade of Gaza since 2007, the year Hamas seized the strip from Abbas' government.

El-Sissi said the conference sent a message that "the status quo must not continue, cannot be returned to, and that any attempt to bring about temporary stability will not last long."

"I tell the Israelis, both citizens and government: The time has come to end the conflict without further delay, to grant rights and establish justice so that prosperity and security can prevail," the Egyptian leader said.

Palestinian-Israeli peace talks have broken down, and Abbas used the conference to warn that the failure to reach a deal posed a serious threat to regional stability.

"Israel's aggression on the Gaza Strip exposed the fragility and dangerous nature of the situation in our region in the absence of a just peace," Abbas said. He called on the international community to support his bid to get the U.N. Security Council to dictate the ground rules for any future talks with Israel, including by setting a deadline for an Israeli withdrawal from Palestinian lands.

The EU's Ashton appeared to back the arguments of Abbas and el-Sissi that work must begin to reach a comprehensive settlement for the Palestinian-Israeli conflict.

"I want to stress one more time that the solution for Gaza cannot be found in Gaza alone," she said. "Only a credible resumption of the peace negotiations can allow for a durable solution to the current crisis."

"This must be the last time in which the international community is called upon to rebuild Gaza. There cannot be a return to the status quo which has proved unsustainable," she added.

Associated Press Writer Bradley Klapper in Cairo contributed to this report.