Egypt's armed forces issued a statement on state television Monday, giving the clashing political forces in the country 48 hours to resolve their problems.
The army said it would have to announce a "new roadmap for the future" if Egyptian President Mohamed Morsi and his opponents did not reach an agreement.
According to a version of the statement translated by NPR, the armed forces said:
The Armed Forces will not take part in the policy making and will not accept a role outside of the democratic framework set by the people.
The nation’s national security is under threat following the latest developments, each side should exhibit responsibility.
The key excerpts are:
The Armed Forces renews its call and give the political forces a 48 hour ultimatum as a last chance to carry the burdens of this historic situation that the nation is going through.
The Armed Forces calls upon everyone that if the people’s demands aren’t set within the timeframe, based on its historic and national obligation it will have to declare a roadmap and procedures that oversee to include all mainstreams including the youth who started this glorious revolution without excluding anyone.
"We understand it as a military coup," one adviser to Morsi told The New York Times. "What form that will take remains to be seen."
The army's statement was greeted mostly with celebrations on the streets of Egypt.
The ultimatum would leave Morsi with few options, including resigning, calling early elections, sharing power or rallying his supporters.
Earlier Monday, the Egyptian opposition had issued an ultimatum of its own, calling on Morsi to resign by Tuesday or face more civil unrest after millions of mostly peaceful anti-government protesters took to the streets across the country Sunday night.
"We give Mohamed Morsi until 5 p.m. (local time) on Tuesday, July 2, to leave power, allowing state institutions to prepare for early presidential elections," the Tamarod (rebel) movement, the group behind Sunday's protests, said on its website.
If not, "Tuesday, 5 p.m. will be the beginning of a complete civil disobedience campaign," the Tamarod added, saying it has collected more than 22 million petition signatures for Morsi's removal.
Some officials in Morsi's administration have already resigned. Tourism minister Hisham Zaazou, communication and IT minister Atef Helmi, minister for parliamentary affairs, Hatem Bagato, and environment minister Khaled Abdel-Aal left the cabinet on Monday.
Following the army's ultimatum, military helicopters were seen flying over Cairo, trailing Egyptian flags:
Last night's protests in Cairo's Tahrir Square and Egypt's second largest city, Alexandria, were by all accounts the largest since the Arab Spring's revolution ousted Hosni Mubarak more than two years ago.
According to the BBC, at least eight people died in clashes. An unidentified security source told Reuters that 17 people had died since Sunday.
While Morsi was not heard or seen during Sunday night's protests, his spokesman, Ehab Fahmy, told reporters that the president was willing to speak with the opposition.
"Dialogue is the only way through which we can reach an understanding... The presidency is open to a real and serious national dialogue," he said.
Morsi, in an interview with the Guardian, remained defiant before the protests and rejected calls for early presidential elections.
"If we changed someone in office who [was elected] according to constitutional legitimacy — well, there will be people opposing the new president too, and a week or a month later they will ask him to step down," Morsi told the Guardian newspaper on Sunday.
The opposition claims Morsi, Egypt's first democratically elected president, has failed to solve the nation's economic problems — resulting in high inflation and low fuel supplies — and tried to establish conservative Islamic laws.