CAIRO

Egypt’s ruling military council pledged today to honor its promise to hand over power to the newly elected president by the end of this month, hours after Islamist candidate Mohammed Morsi claimed victory in the first free presidential vote since the ouster of authoritarian leader Hosni Mubarak 16 months ago.

Maj-Gen. Mohammed al-Assar, a senior member of the ruling council, said the generals would transfer power in a “grand ceremony,” according to the state news agency. He did not give an exact date or mention Morsi by name.

He said the new president will have the authority to appoint and dismiss the government and that the military council has no intention of taking away any of the president’s authorities.

But the military council issued an interim constitution just as polls were closing late Sunday night that gave the generals sweeping authority to maintain their grip on power and subordinate the nominal head of state.

Though official results have not yet been announced, the Brotherhood released a tally that showed Morsi of the Muslim Brotherhood took nearly 52 percent of the vote to defeat Mubarak’s last Prime Minister Ahmed Shafiq with about 48 percent in a very close race. The count was based on results announced by election officials at individual polling centers, where each campaign has representatives who compile and release the numbers before the formal announcement.

If Morsi’s victory is confirmed in the official result expected on Thursday, it would be the first victory of an Islamist as head of state in the stunning wave of prodemocracy uprisings that swept the Middle East the past year. But the military’s last minute power grab sharpens the possibility of confrontation and more of the turmoil that has beset Egypt since Mubarak’s overthrow.

By midday, several hundred flag-waving supporters had gathered at Cairo’s Tahrir Square, the birthplace of the uprising, to celebrate.

In a victory speech at his headquarters in the middle of the night, Morsi, 60, clearly sought to assuage the fears of many Egyptians that the Brotherhood will try to impose stricter provisions of Islamic law. He said he seeks “stability, love and brotherhood for the Egyptian civil, national, democratic, constitutional and modern state” and made no mention of Islamic law.

“Thank God, who successfully led us to this blessed revolution. Thank God, who guided the people of Egypt to this correct path, the road of freedom, democracy,” the bearded, U.S.-educated engineer declared.

Just a few days before the presidential runoff on Saturday and Sunday, the military granted itself broad new powers to arrest civilians and a court packed with judges appointed by Mubarak dissolved the parliament freely elected after the uprising, which was dominated by the Muslim Brotherhood.

The interim constitution announced late Sunday declared the military rulers the country’s lawmakers in lieu of the dissolved parliament, gave them control over the budget and the power to determine who writes the permanent constitution that will define the country’s future.

The military was thought to be very concerned about having to submit its budget to civilian oversight under an elected parliament and president because it is estimated to control 20-40 percent of Egypt’s economy.

The Brotherhood challenged the military’s power grab, saying Sunday it did not recognize the dissolution of parliament. It also rejected the military’s right to issue an interim constitution and oversee the drafting of a new one.

That set up a potential power struggle over spheres of authority between Egypt’s two strongest forces — the military and the Brotherhood. The fundamentalist group has campaigned on a platform of bringing Egypt closer to a form of Islamic rule. But the military has positioned itself to block that.

And whether the Brotherhood will push a fight remains an open question. It has reached accommodations with the military in the past.

At Brotherhood campaign headquarters, officials and supporters were ebullient. The group was banned for most of its 80-year history and repeatedly subjected to crackdowns under Mubarak’s rule.

The 18-day uprising was launched by secular, leftist young activists, joined only later by the Brotherhood’s leadership as millions took to the street, seeking an end to an authoritarian regime considered hopelessly corrupt.

Morsi, who just before the two days of voting declared he “loves” the military, did not make a show of defiance against the generals. Still, the speaker of the dissolved parliament, Brotherhood member Saad el-Katatni, stood next to him in a sign of the group’s insistence the legislature remains in place.

Some in the Brotherhood were ready for a challenge. “Down with military rule,” the supporters chanted at the headquarters. The secular revolutionary group April 6, which helped launch the anti-Mubarak uprising, congratulated the Brotherhood on its win.

“The next phase is more difficult. We must all unite against the oppressive rule of the military council,” one of its founders, Ahmed Maher, said.