Under the Palestinian agreement, the two sides agreed to form a "national consensus" government under Abbas within weeks.
However, this was not the first unity agreement between the rival factions.
Hamas and Abbas' Fatah, the central faction of the PLO, already signed reconciliation deals in Cairo (2011) and Doha (2012), aimed at ending the political division between the Gaza Strip and the West Bank.
Neither accord was implemented.
And many Palestinians doubt that the latest reconciliation move will succeed because of "previous bad experiences", said Mkhaimer Abu Saada, a political science professor also at Al-Azhar University, adding that the deal will be "hard to implement".
In addition to a furious Israel mulling punitive measures against the Palestinian Authority, Washington was both "disappointed" and "troubled" by the fresh agreement, with a State Department spokeswoman warning that "there would be implications".
Any Palestinian government must commit "unambiguously" to the principles of non-violence and to the existence of Israel, State Department spokeswoman Jen Psaki said, referring to Hamas' refusal to recognise Israel and advocating an armed struggle against it.
Jibril Rajub, a Fatah leader, told AFP "the next national consensus government will proclaim loud and clear that it accepts the Quartet's conditions".
The Middle East Quartet - the European Union, the United Nations, Russia and the United States - demands that Hamas recognise Israel and existing agreements between it and the PLO, and renounce armed struggle.
Analysts say the Islamist Hamas Government, besieged in Gaza and outlawed in Egypt, has an interest in reconciliation.
Hamas' fortunes have slipped since last July, when the Egyptian army deposed the movement's ally, President Mohamed Morsi of the Muslim Brotherhood.
And Egypt's military has since destroyed hundreds of the tunnels through which not only weapons and ammunition were smuggled, but also commodities and construction materials.
"The [Palestinian] division became really harmful to Hamas after the Muslim Brotherhood loss in Egypt and its dire financial situation," Sharab said.
The destruction of the tunnels has generated losses estimated at US$230 million ($268.5 million) by the admission of the Hamas Government, which is struggling to pay its civil servants.
"Hamas wants to escape Egyptian pressure.
"Reconciliation is its window to improve its regional and Arab relations, particularly with Egypt," the political scientist said.
The Islamist movement "is closer to political pragmatism in dealing with the negotiations" between Abbas and Israel, Sharab said.
Ashraf Abu al-Houl, deputy editor of Egypt's Al-Ahram newspaper, thinks "Egyptian pressure pushed Hamas to sit at the table and reconcile".
- AFP
