Anti-regime protesters vowed to crank up pressure on Egypt's caretaker junta on Friday with a "million man march" in Cairo's Tahrir square.
Friday's planned show of mass opposition comes at the end of a week of protests against army rule that have left 41 people dead.
Protests after Friday afternoon Muslim prayers have been some of the largest and most explosive during the so-called Arab Spring that now draws into an Arab Winter.
A truce between security forces and hard-line protesters brought a nervous calm to the streets near Tahrir on Thursday after five days of clashes that turned part of the capital into a battle zone and left residents choking in clouds of tear gas.
But Egypt's military leader Field Marshal Hussein Tantawi's decision to tap former Mubarak-era prime minister Kamal Ganzouri to form a new government has ratcheted up tensions in Cairo's streets.
The caretaker junta said it was doing all it could to prevent more violence, offered condolences and compensation to families of the dead, and a swift enquiry into who caused the unrest.
But protesters, who say the military is dragging its feet, are calling for blood.
"The people demand the execution of the marshal," crowds chanted on Thursday, referring to Tantawi.
The protests come as Egypt finds an economy that was stable throughout the Mubarak era in a tailspin. In recent days, the Egyptian central bank increased interest rates, the pound weakened to more than six to the dollar, and Standard & Poor's slashed Egypt's credit rating.
In a statement on its Facebook page, the interim junta said it was "appealing to protesters to cancel the demonstration," saying it wanted to avoid divisions.
Fears the army will continue to wield power behind an elected civilian administration has grown in recent weeks as the government and opposition parties wrangled over a new constitution.
The interim junta originally promised to cede power to a civilian government within six months of the fall of Mubarak, but then set its own timetable for elections, drawing up the constitution, and choosing a new president that would draw out its rule until 2013.