Egypt's military is giving President Mohamed Morsi and opposition leaders 48 hours to settle their differences and agree on a path forward.
Defense Minister General Abdel Fattah al-Sisi issued the ultimatum Monday, after violent protesters ransacked the Cairo headquarters of Mr. Morsi's Muslim Brotherhood.
Witnesses said the protesters smashed windows and tossed firebombs while Muslim Brotherhood guards defended the building with gunfire. Officials said at least five people were killed, bringing the nationwide death toll to 16 since Sunday.
Al-Sisi said if the politicians fail to reach an agreement, the military will present its own road map for Egypt's future.
Earlier, opposition organizers said they were giving President Morsi until 5 p.m. Cairo time on Tuesday to resign.
Anti-government demonstrations in Egypt on Sunday were the largest since the 2011 revolution that swept former president Hosni Mubarak from power. Arabic-language media quoted the Interior Ministry saying the crowds in Cairo and other cities across Egypt totaled as many as 3 million people.
Some protesters remained in Cairo's Tahrir Square overnight and some, like Jamal Helal, vowed not to back down.
SOUNDBITE: (Arabic) Jamal Helal, anti-Morsi protester // from Egypt Tension 2- 898615 ))
"Don't you (Morsi) see that the country is sinking? You should understand that. You also should understand that people don't want you any more. Be fair."
As tensions mounted Sunday, the presidential office issued a statement saying dialogue is the only way out of Egypt's political crisis.
In an interview published in the British newspaper The Guardian, President Morsi said that if he gave in to the pressure, a new president could face similar opposition demands to quit after a "week or a month."
Egypt's military has warned both sides to resolve their differences through negotiations but neither the military nor the police intervened when protesters stormed the Muslim Brotherhood headquarters in Cairo.
Since last week, supporters and opponents of President Morsi have been engaging in sporadic and sometimes deadly clashes.