The two largest Palestinian factions Hamas and Fatah are due to end a four-year rift at an official ceremony in Egypt on Wednesday.
The Palestinian president Mahmoud Abbas and Hamas leader Khaled Meshaal have already arrived in Cairo ahead of the event.
Last week Egypt brokered the deal between the Islamist Hamas which runs the Gaza strip, and the secular Fatah which heads the Palestinian Authority and controls self-rule areas of the Israeli occupied West Bank.
Palestinians see the reconciliation as crucial in their campaign for an independent state. But Israel has denounced the deal, saying Fatah must choose between it and Hamas.
The Israelis refuse to negotiate with Hamas, considering it to be a terrorist organisation. They fear the agreement will boost Hamas’ standing.
Representatives from several Palestinian factions met to sign the accord on Tuesday.