The Fatah official stressed that President Mahmoud Abbas instructed the delegation not to return without a reconciliation deal. Over the past few weeks, Palestinian Premier Rami Hamdallah with the government travelled for the first time in over two years to Gaza to start procedures to gain control of the Strip.
Abbas welcomed the deal in comments to AFP and said he considered it a "final agreement to end the division" - though many details remain to be resolved and previous reconciliation attempts have repeatedly failed.
Details of the deal were announced at a news conference in Cairo, where the negotiators were meeting.
Hamas seized Gaza from Fatah in a near civil war in 2007 and the two factions have been at loggerheads ever since.
The official was referring to the diplomatic Quartet on Middle East peace, which includes the United Nations, the United States, the European Union and Russian Federation.
The deal, reportedly concluded at dawn this morning, includes a provision for Gaza to be handed over to a unity government, led by Fatah, by December 1.
'Marvel's Runaways' Trailer: Hulu Brings 'Gossip Girl' Flair to the Marvel Universe
Judging by the trailer, the show draws its influences from late-nineties in movies like The Craft and The Faculty . Marvel's Runaways Josh Schwartz , Stephanie Savage , Jeph Loeb , Jim Chory, and Lis Rowinski.
Faced with increasing isolation and a severe electricity shortage, Hamas has reached out to Cairo for help, hoping to have the Rafah border with Egypt opened.
Over the past decade, each side deepened control over its territory, making it increasingly hard to forge compromises, and repeated attempts at reconciliation failed.
With Hamas in control, conditions in Gaza deteriorated.
The crossing has remained largely closed in recent years.
A major sticking point has been the Hamas military wing and its arsenal, which Hamas has said is not up for discussion.
"Israel will examine developments in the field and act accordingly", said a statement from Prime Minister Benjamin Netanyahu's office. Israel and Egypt imposed a blockade on the territory, severely restricting Palestinians from leaving the territory and goods from entering.