Khalil Assaf, who heads a Palestinian forum of independent figures, said Monday Hamas would hold a 25th anniversary festival, including speeches from leaders, Thursday in Nablus.
Monday's announcement followed a similar gesture by Hamas, which has approved a Fatah festival in Gaza to commemorate the group's 48th anniversary, Ma'an News Agency reported.
Bitter fighting led the two parties to split Palestine into separate governments in 2007, and both clamped down on political activities and celebrations by the rival party, Ma'an reported.
The groups could be on their way to agreement, though, as PA President Mahmoud Abbas announced Sunday he planned to go to Cairo soon to take part in reconciliation talks, The Jerusalem Post reported.
"Reconciliation [with Hamas] is dear to us and the unity of our people," Abbas said.
"Responsibility for Palestine is bigger than one faction alone... Hamas cannot do without Fatah and Fatah cannot do without Hamas," Hamas leader Khaled Mashaal said.