An Obama administration official, speaking on the condition of anonymity, shrugged it all off as empty talk, saying, “There is zero chance this happens.”

Egyptians were far more concerned about the spectacle of the speech in Tahrir Square — the proving ground of the country’s revolution — as the latest power play in the standoff between the Muslim Brotherhood and the ruling generals over Egypt’s future.

“I come to you as the source of legitimacy,” Mr. Morsi declared, pointedly pledging his allegiance to the public and eschewing the institutions of the government of his ousted predecessor, Hosni Mubarak. “Everyone hears me, all the people and the cabinet and government, army, police. There is no authority over this authority. You have the power!”

His soaring talk of popular sovereignty, however, appeared to be an attempt to cover up for an early concession to the generals, who still cling to power.

On the eve of Mr. Morsi’s election, the generals dissolved Parliament, seized its powers and issued a new interim charter depriving the office of Egypt’s president of much of its authority. They also stipulated that the president should swear the oath in front of the Mubarak-appointed judges of the Supreme Constitutional Court.