The Fatah officials who are expected to visit the Strip include Nabil Sha'ath, Jibril Rajoub, Mahmoud al-Aloul and Fakhri Bsaiso.
The sources said that Mashaal has agreed to sign a "reconciliation accord" with Fatah after the Egyptians promised to permanently reopen the Rafah border crossing between Sinai and southern Gaza.
They said the agreement would be signed before the end of the year.
The Rafah terminal has been formally closed since Hamas seized control of the entire Gaza Strip in the summer of 2007. Under pressure from human rights groups and many Arabs, the Egyptians occasionally open the border crossing for a day or two for "humanitarian cases."
Cairo's pledge to reopen the border crossing on a permanent basis is seen as a significant victory for Hamas, which has been struggling hard in the past few years to end the blockade on the Gaza Strip.
According to the sources, Hamas and Fatah are very close to reaching agreement over the reconstruction of the Palestinian security forces under the supervision of Arab countries.
Again, this is seen as an achievement for Hamas, which has long been demanding an end to Fatah's exclusive control over the Palestinian Authority security forces.