Egypt's army chief General Abdel Fattah al-Sissi warned today that the state could collapse if the political crisis drags on.
It was a stark message from the military, which ran the country up until elections last year.
Egypt's armed forces are its largest institution and wield vast economic power.
President Mohamed Morsi ordered the army to take control of the Suez Canal cities of Port Said and Suez on Sunday night and declared a 30-day state of emergency.
Troops deployed in the two riot-torn cities stood by and watched on Monday night as thousands defied a 9pm curfew and took to the streets.
Gen Sisi, who is also Egypt's defence minister, said that the continued political conflict "could lead to the collapse of the state and threaten future generations."
He said the military faced a "grave predicament" when weighing up citizens' rights and its task of protecting government facilities.
It was the military's first public comment since the crisis erupted last week on the second anniversary of Egypt's revolution.
Tanks took up positions in Port Said today as six more funerals took place for people killed in clashes, with thousands marching against Mr Morsi.
"Leave, leave," they chanted.
In Cairo, the area around Tahrir Square was relatively quiet, with only intermittent clashes between police and rock-throwing protesters at the Qasr el-Nile bridge.
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