CAIRO – In front of tens of thousands of cheering supporters, Egypt’s first Islamist and civilian president-elect vowed Friday to fight for his authority and symbolically read an oath of office on Cairo’s Tahrir Square on the eve of his official inauguration.

Mohammed Morsi’s strongly worded speech was a show of defiance as he gears up for a power struggle with the country’s ruling generals, who passed a constitutional declaration taking over major presidential powers in the days before election results were announced after a bitter campaign.

“Everybody is hearing me now. The government, the military and the police. ... No power above this power,” he said as the crowd roared. “I reaffirm to you I will not give up any of the president’s authorities. I can’t afford to do this. I don’t have that right to that.”