Without mentioning Hamas's refusal to recognize Israel, Ban "strongly" appealed to all the Palestinian parties to commit to the principles of the diplomatic Quartet on Middle East peace, his spokesman said.
UN Special Coordinator for the Middle East peace process Robert Serry will attend the Cairo ceremony, UN spokesman Martin Nesirky said.
"The secretary general has continually supported efforts for unity and the work of Egypt and President Abbas in this regard," Nesirky said.
Ban feels there has to be "unity" as well in the positions of the Quartet the United States, Russia, the European Union and the United Nations and the commitments of the Palestine Liberation Organization, he added.
The Quartet has set out a roadmap to a Palestinian-Israeli peace accord that calls on Palestinian groups to renounce violence and recognize Israel's right to exist.
"The secretary general therefore strongly appeals to all Palestinian parties to commit to these principles," Nesirky said.
The United States has also said that any Palestinian government emerging from the accord must accept the Quartet principles.
Fatah, Hamas and 11 other factions signed a reconciliation deal in Cairo on Tuesday to end the divide between the West Bank and Gaza and hold elections in a year.
Israel has called the deal a blow to peace because of the inclusion of Hams.