The National Salvation Front, the largest opposition bloc, rejected the constitutional declaration. It said it had not been consulted prior to the announcement and demanded changes in the decree.
“One cannot construct a building without foundation, or a nation without legitimacy and representation,” said Gehad el-Haddad, a Muslim Brotherhood spokesman.
The Muslim Brotherhood had been banned in Egypt since 1954, but its candidates participated in elections as independents. After longtime President Hosni Mubarak was ousted in Arab Spring pro-democracy protests in February 2011, the Brotherhood said it would not participate in elections, but later reneged on that pledge.
The Tamarod movement, which was behind last week’s protests, expressed concern about the Islamist elements in the decree and said the extraordinary powers given to the president set the stage for a new dictatorship.
“We were surprised by it, just like everyone else,” Mahmoud Badr, a spokesman for the Tamarod movement, wrote on his official Facebook page.
The ultraconservative Al-Gamaa Al-Islamiya said it would not accept the declaration because it was issued by an appointed, rather than an elected, president.
Mr. Mansour, chief justice of the Constitutional Court, was sworn in as interim president last week.
Mr. el-Biblawi served as finance minister in an interim Cabinet that followed Mr. Mubarak’s ouster in pro-democracy Arab Spring protests in February 2011.
Saudi Arabia and the United Arab Emirates, meanwhile, announced that they will provide $8 billion in aid to Egypt.
On Tuesday night, thousands of pro-Morsi supporters held mock funeral processions in Cairo’s Nasr City district. Some gathered outside the U.S. Embassy in Cairo to protest U.S. support for the Egyptian military.
The U.S. provides $1.3 billion in aid to the Egyptian military. That aid could be cut off under U.S. law if it is determined that Mr. Morsi’s ouster was a military coup. The Obama administration said this week that it would not be in U.S. interests to cut off that aid.
Some lawmakers have called for the aid to be cut off.
That would be a mistake, said Mr. Trager.
“What Washington has to be most attentive to is trying to end the civil strife in Egypt as soon as possible, because if that spirals out of control then it will be even harder to come up with a political formula that will get Egypt on the right path again,” he said.