The vote Saturday is expected to draw 25.5 million voters in 17 governates, about half of Egypt's eligible voters, in the second phase of the national referendum on the country's first post-uprising constitution, the news website Ahram Online reported Friday.

The first phase of the referendum Dec. 15 -- in 10 governorates -- had about 57 percent voting in favor of the draft, unofficial results indicated.

Egyptian President Mohamed Morsi and his Islamist allies said the charter is essential to Egypt's transition to democracy 22 months after the fall of President Hosni Mubarak.