Opponents of an Egyptian military declaration seeking to curtail the powers of the next president are to stage a mass demonstration in Cairo.
The Muslim Brotherhood, whose candidate Mohammed Morsi claimed victory in the presidential run-off, will join the protest with other political groups, according to campaigners.
Spokesmen for Mr Morsi said the protest is planned for Tahrir Square, birthplace of the uprising that toppled Hosni Mubarak's regime 16 months ago.
The protest is also to denounce a court ruling that dissolved parliament, where the Brotherhood dominated with almost half the seats.
One of the main liberal youth groups behind the uprising, April 6, said it will also take part in the protest.