By Tamim Elyan and Alastair Macdonald
CAIRO (Reuters) - Egyptians find out on Sunday whether their next president will be a former military officer or an Islamist from the army's old adversary, the Muslim Brotherhood, after a long week's wait since a vote to pick a successor to the deposed Hosni Mubarak.
Impatient Brotherhood supporters have been out on Cairo's Tahrir Square day and night since a call in midweek from their leaders to demand the current ruling generals cancel measures they say are designed to hem in the powers of the man they believe was elected last weekend, Islamist Mohamed Morsy.
Hundreds were there again on Saturday, chanting "Victory for Morsy!" and "Morsy, Morsy, Allahu akbar!" (God is greatest), before officials finally set a time for announcing the result.
The election committee will do so at news conference at 3 p.m. (9.00 a.m. EDT) on Sunday, committee official Hatem Bagato said on Saturday, after run-off voting was held on June 16-17.
The party atmosphere in the square anticipated what could be one of the most dramatic turns of events in the Middle East in decades - the emergence of an Islamist president of the most populous Arab nation.
A delay in announcing the result, initially scheduled for Thursday, was explained by officials as required to deal with appeals over local voting irregularities. But it has prompted Brotherhood concern that the military-led "deep state", left over when Mubarak was toppled last year, was trying to steal their victory, just as it routinely rigged votes in the past.
"We want the military council to announce the real results without forgery," said Hassan Eissa, 43, an accountant from north of Cairo who was demonstrating on the square. He accused the army of reneging on promises to hand over when it dissolved the Islamist-led parliament on the eve of the presidential run-off and then took for itself legislative powers by decree.
"They have no right," Eissa said. "Egyptians shouldn't be under any kind of guardianship after the revolution."
A Morsy win would create a dramatic new configuration for Egypt's politics. Supporters of religious rule will be delighted but others, including many who fought on Tahrir Square to end dictatorship, will be anxious at what it means for minorities, women, secular values and Egypt's dealings with the West.
Reformist politician Mohamed ElBaradei said he had been in contact with the military and Morsy's camp to avoid a showdown, but said he was worried that if Shafik were declared winner "we are in for a lot of instability and violence ... a major uprising." His comments were carried by the CNN website.
Violence by hardline Islamists in Tunisia, whose revolt inspired that in Egypt, has troubled many Egyptian liberals.
On Saturday, a group of liberal and leftist groups announced the formation of an alternative "civil front", seeking support from those wanting neither military nor religious rule.
"Those who are attacking the military council, have allied with it when their interests were in line," said Ahmed Said, head of the liberal Free Egyptians Party, noting links between the Muslim Brotherhood and ruling generals in the past year.
Senior figures from both the Supreme Council of the Armed Forces (SCAF) and the Brotherhood told Reuters they had been in discreet talks this week on political arrangements, though the army has made clear it will not go back on what critics called a "soft coup" aimed at delaying a handover to full civilian rule.
It will neither cancel the dissolution of the Islamist-led parliament nor a decree by which it reserved legislative powers for the council, curbing the president's power.
Presented with a take-it-or-leave-it choice, the Brotherhood may find a compromise to pull their protesters off the streets. Years of conflict have made it a wary organization, and it has cooperated with the council in the 16 months since Mubarak fell.
Electoral and military officials told Reuters during the week and as late as Friday that the Brotherhood candidate had a narrow but clear lead over former general Ahmed Shafik, Mubarak's last prime minister. But nothing is certain.
One newspaper, Shorouk, headlined: "Morsy to be announced president today ... Unless."
Morsy, like Shafik, has promised to build a government that brings in people from across the political spectrum. Many of those who launched the Arab Spring uprising were dismayed when more centrist candidates, neither from the army nor the Brotherhood, were eliminated in the first round vote last month.
While some grudgingly backed Shafik to block religious rule, others half-heartedly supported Morsy to prevent what they saw as a return to the old regime. Among those protesting on Tahrir Square on Saturday, Cairo lawyer Atef Rehan said: "I'm not from the Brotherhood and I voted for Morsy only reluctantly.
"But I am here to support their demands."
A 60-year-old, U.S.-educated engineer, the bearded and bespectacled Morsy is not a familiar figure to Egyptians, some of whom ridicule him as the movement's "spare tire" after his campaign was launched following the exclusion from the race on a technicality of a much better known leader, Khairat al-Shater.
Both sides recall the bloodshed that ravaged another North African state, Algeria, when military rulers thwarted an Islamist movement's triumph at the ballot box in the 1990s, and appear willing to renew the tentative cooperation they built up after Mubarak's overthrow and step back from an outright clash.
An Islamist insurrection in Egypt in the 1990s also cost hundreds of lives. That uprising was not supported by the Brotherhood, which renounced violence decades ago as a means to achieve political change in Egypt.
Delay in the final tally of votes was due to many appeals being heard by the electoral commission, officials said. But it also gave more time for talks to defuse tensions.
Discussions between generals and Islamists, whose violent confrontation has marked Egypt for decades, were assuming Morsy would win narrowly.
"We have met with them to discuss how to get out of this crisis after parliament was dissolved and the new president's powers curbed," Shater, who runs the Brotherhood's finances and strategic planning, told Reuters - although he added they were some way from reaching any kind of agreement.
Major General Mamdouh Shaheen, a member of SCAF, confirmed the recent meetings and repeated the army's commitment to a democratic transition. But he echoed a strong statement issued by SCAF on Friday that rejected the Brotherhood's demands.
"The constitutional decree is the exclusive authority of the military council," Shaheen told Reuters.
In a brusque statement read on state television as Egyptians were completing their Friday prayers, SCAF criticized the Brotherhood's premature announcement of the election result and said protesters must not disrupt daily life.
Morsy shot back that the generals were defying the will of the people and said protests would go on. But he praised the army as "patriotic" and urged a rapid election result.
In a country where virtually no one can remember an election before last year that was not rigged, trust is low, not least among Brotherhood officials, many of whom, like Morsy, were jailed under Mubarak for their political activities.
The same electoral commission that handed 90 percent of a November 2010 parliamentary vote to Mubarak's supporters - a result that fuelled the protests that brought him down a few weeks later - sits in judgment on the new presidency.
(Additional reporting by Marwa Awad; Writing by Alastair Macdonald; Editing by Edmund Blair)