The United States is promising 212 million dollars (£132m) in immediate assistance to the Palestinians as part of an international effort to rebuild the Gaza Strip after this summer's 50-day war.
US secretary of state John Kerry said people in Gaza "need our help desperately - not tomorrow, not next week, but they need it now".
He announced the new money at a donor conference for the Palestinians in Cairo.
The Palestinians are seeking 4 billion dollars (£2.5bn) in international aid.
Palestinian president Mahmoud Abbas promised a transparent and responsible use of funds pledged at the conference.
Mr Abbas said the latest Gaza war caused what he described as "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 UN, the donors, international financial institutions, civil society and the private sector," he said.
Mr Abbas and the militant Hamas group, which has ruled Gaza since 2007, recently formed a reconciliation 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.
Egyptian president Abdel-Fattah el-Sissi, whose government negotiated the ceasefire that ended the war, strongly suggested in his opening address that Hamas would not play a leading role in the reconstruction effort.
Donors plan to funnel the aid through the Palestinian Authority that Mr Abbas leads, and bypass Hamas.
The reconstruction effort, said Mr el-Sissi, hinged on a "permanent calm" between Hamas and Israel, and required the exercise of "full authority" by the Palestinian Authority led by Mr 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 Mr Abbas in the West Bank. Egypt and Israel have enforced a blockade of Gaza since 2007, the year Hamas seized the strip from Mr Abbas' government.
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.
Both Mr Abbas and Mr el-Sissi said an Arab peace plan adopted in 2002 provided a basis for settling the Palestinian-Israel conflict. The plan envisages Israel's withdrawal from Arab territories it occupied in the 1967 Middle East war in return for normalised relations with all Arab nations.