Thousands of Egyptians demanding an end to military rule converged on Cairo's Tahrir square on Friday in what activists say was the biggest day yet of protests in a week of violence that has seen at least 41 people killed.
The generals who have governed Egypt since people power toppled president Hosni Mubarak are facing a major challenge to their authority.
Activists who accuse them of trying to cling to power once again turned Tahrir into a centre of mass demonstrations, producing scenes similar to the uprising that toppled Mubarak.
Since last Saturday, streets near Tahrir have become battle zones with stone-throwing protesters fought police firing tear gas, pellets and rubber bullets, although a truce on Thursday calmed the violence in the past 24 hours.
Activists sought to bring a million people into the streets of the capital on what they have dubbed "the Friday of the last chance". The weekly Muslim prayer day has traditionally produced the biggest demonstrations of the Arab Spring revolts sweeping across West Asia.
The ruling military council has confirmed that it had appointed Kamal Ganzouri, who served as prime minister under Mubarak from 1996-99, to head an interim cabinet. Prime Minister Essam Sharaf's government resigned this week.
The military rulers say they will transfer power to civilians, but the process should not be rushed to avoid chaos.
Washington, long a bedrock supporter of Egypt's military, called on the generals on Friday to step aside "as soon as possible" and give real power to the new cabinet "immediately".
"Full transfer of power to a civilian government must take place in a just and inclusive manner that responds to the legitimate aspirations of the Egyptian people, as soon as possible," White House spokesman Jay Carney said in a statement.