"A certain number of detainees will be freed right at the beginning of the dialogue," said the statement from Azzam al-Ahmad, leader of the Fatah bloc in the Palestinian parliament, and Mahmoud Zahar, a senior Hamas official.
Hamas members freed
The statement said: "Other detainees will be freed successively so that this issue will be totally closed before the end of the national Palestinian dialogue.”
Zahar said 80 Hamas members held in the West Bank, which is controlled by Fatah, have been released and that 300 were still being held.
A planned unity government by Fatah and Hamas will deal with foreign governments, co-ordinate reconstruction in the Gaza Strip and prepare for Palestinian presidential and legislative elections.
Nasser al-Shorafa, a Palestinian resident of Egypt, told Al Jazeera: "The crossing points are the main lifeline to Palestinians. With the gates closed, families have been separated and people starved."
"This should be at the centre of the talks," he said.
Fatah, the secular group headed by Mahmoud Abbas, the Palestinian president, and Hamas have long been rivals but their feuding boiled over in June 2007 when Hamas seized control of the Gaza strip.
Thursday's conference, which will also bring in other Palestinian factions, stems from Egyptian proposals for a lasting ceasefire following Israel's 23-day onslaught on Gaza.
More than 1,300 people were killed and buildings and infrastructure destroyed.