Egypt has served as mediator since Hamas militants captured an Israeli soldier, Gilad Schalit, near Gaza in June 2006. Hamas demands the release of hundreds of Palestinians by Israel, in exchange for Schalit.
German diplomats have become involved in the negotiations in recent weeks, making 11 trips to Hamas-ruled Gaza in the past month, said Ayman Taha, a Hamas spokesman. German mediators have helped arrange swaps involving Israeli captives in the past, and Taha described the German effort as "serious."
However, there have been many false alarms about an imminent swap, and there were no concrete signs of progress Saturday.
Mashaal, the top Hamas leader based in Damascus, was to arrive in Cairo later Saturday, Taha said.
Hamas officials gave conflicting reports on Mashaal's mission. Some said he was only to discuss the internal Palestinian conflict with Egyptian counterparts, while others said the prisoner swap is also on the agenda.
Hamas seized Gaza by force in June 2007, ousting forces loyal to pragmatic Palestinian President Mahmoud Abbas and leaving him only in control of the West Bank. A Palestinian unity deal is seen as a prerequisite for an eventual Mideast peace agreement, but months of reconciliation talks have yielded little progress.