An Egyptian girl waves a national flag Sunday while supporters of Egypt’s ousted President Mohammed Morsi chant slogans against the Egyptian Army at a sit-in at Rabaah al-Adawiya mosque, which is fortified with multiple walls of bricks, tires, metal barricades and sandbags, and where protesters have installed their camp in Nasr City, Cairo, Egypt.

The Egyptian police were preparing to move at dawn today to choke off two sit-ins where tens of thousands have gathered to protest Morsi’s ouster, Interior Ministry officials said Sunday night, vowing to gradually press further until the demonstrators dispersed.

The new military-appointed government has promised for more than a week to use all necessary force to clear out the sit-ins, which were established by Morsi’s Islamist allies in the Muslim Brotherhood upon his ouster nearly six weeks ago. But until now, a combination of external pressure from Western powers and internal dissent from liberal Cabinet ministers had appeared to persuade Gen. Abdel-Fattah el-Sissi, the officer who ordered the takeover, to hold off decisive action.

It remained possible Sunday night that the latest pledge to clear out the sit-ins might also fail to materialize. But if it proceeds, human rights advocates said, the police action could lead to the loss of dozens of lives, in part because, they say, the Egyptian police are incapable of a gradual escalation — especially if they meet any friction or resistance.