CAIRO – Protesters holding sticks and wearing helmets and makeshift body armor stand behind mounds of sandbags, tires and brick walls. They change guards every two hours to ensure they stay alert.

With Egypt’s military-backed government signaling a crackdown is imminent, supporters of ousted Islamist President Mohammed Morsi are taking no chances with security at their two protest camps in Cairo.

On Wednesday, the Cabinet ordered the police to break up the sit-ins, saying they pose an “unacceptable threat” to national security.

Interior Minister Mohammed Ibrahim said the order will be carried out in gradual steps according to instructions from prosecutors. “I hope they resort to reason” and leave without authorities having to move in, he told The Associated Press in a telephone interview.

Ahmed Sobaie, spokesman for the Muslim Brotherhood’s political arm, the Freedom and Justice party, derided the Cabinet decision as “paving the way for another massacre.”

In Washington, State Department spokeswoman Marie Harf appealed to the military-led government to avoid violence. “We have continued to urge the interim government officials and security forces to respect the right of peaceful assembly,” she said. “That obviously includes sit-ins.”

Organizers are portraying the sit-ins outside the Rabaah al-Adawiya mosque in eastern Cairo and a smaller one across the city near Cairo University’s main campus as evidence of an enduring support base for Morsi’s once-dominant Muslim Brotherhood.

The Brotherhood has so far refused to cooperate with the country’s interim leaders, whom it calls “traitors,” or participate in a military-backed fast-track transition plan to return to a democratically elected government by early next year. Instead it tries to keep thousands of supporters camped out in tents decorated with photos of Morsi, occupying a cross-shaped intersection facing the mosque.

Authorities have already cracked down on the organization, arresting Morsi and other senior leaders. On Wednesday, Egyptian prosecutors referred three top leaders of the Muslim Brotherhood to trial for allegedly inciting the killing of at least eight protesters last month outside the group’s Cairo headquarters.