General Abdel Fattah al Sisi, appointed by President Mohamed Mursi last year to head the military, added in a statement yesterday that one of the primary goals of deploying troops in cities on the Suez Canal was to protect the waterway that is vital for Egypt's economy and world trade.
General Sisi's comments, published on an official Army Facebook page, followed 52 deaths in the past week of disorder.
It highlighted the mounting sense of crisis that faces Egypt and its Islamist head of state, who is struggling to fix a teetering economy and needs to prepare Egypt for a parliamentary election in a few months that is meant to cement the new democracy.
The comments are unlikely to mean the Army wants to take back the power it held, in effect, for six decades since the end of the colonial period and in the interim period after the overthrow of former general Hosni Mubarak two years ago.
However, it sends a powerful message that Egypt's biggest institution, with a huge economic as well as security role and a recipient of massive direct US subsidies, is worried about the fate of the nation after five days of turmoil in major cities.
Mr Sisi, who is also defence minister, said: "The continuation of the struggle of the different political forces ... over the management of state affairs could lead to the collapse of the state."
He said the economic, political and social challenges facing the country represented a real threat to the security of Egypt and the cohesiveness of the Egyptian state and the Army would remain the solid and cohesive block on which the state rests.
Political opponents spurned a call by Mr Mursi for talks on Monday to try to end the violence.
Instead, huge crowds of protesters took to the streets in Cairo and Alexandria, and in the three Suez Canal cities – Port Said, Ismailia and Suez – where Mr Mursi on Sunday imposed emergency rule and a curfew.
Residents in the three canal cities have demonstrated in defiance of the curfew. At least two men died in fighting in Port Said.
Protests first flared to mark the second anniversary of the uprising that erupted on January 25, 2011, and toppled Mubarak 18 days later.
They have been exacerbated by riots in Port Said by those enraged by a court ruling sentencing people from the city to death over deadly football violence last year.
"Down, down with Mohamed Mursi. Down, down with the state of emergency," crowds shouted in Ismailia.
In Cairo, flames lit up the night sky as protesters set vehicles ablaze.
The demonstrators accuse Mr Mursi of betraying the two-year-old revolution. The President and his supporters in the Muslim Brotherhood accuse the protesters of seeking to overthrow Egypt's first ever democratically elected leader by undemocratic means.
Some activists said Mr Mursi's measures to try to impose control could backfire.
Ahmed Maher of the April 6 movement that helped galvanise the uprising said: "Martial law, state of emergency and Army arrests of civilians are not a solution to the crisis. All this will do is further provoke the youth.
"The solution has to be a political one that addresses the roots of the problem."