The Muslim Brotherhood on Wednesday announced plans to participate in protests Friday after organizers changed protest demands.
The Brotherhood said in a statement it had planned to abstain because the rally was organized primarily to reiterate calls for drafting a constitution ahead of parliamentary elections.
Since then, various movements and groups have decided not to press the "Constitution First" demand on Friday.
The Brotherhood will join the demonstration to condemn a violent security crackdown in Tahrir last week against protesters, including families of some of those killed during the revolution.
Trials for officials accused of killing revolution protesters are proceeding at a provocatively slow pace, as if to reward former President Hosni Mubarak, the Brotherhood said.
The release of officers charged with killing protesters pending investigations allows them to manipulate evidence and pressure victims' families to drop their cases, the statement said.