CAIRO  - Egypt on Thursday braced for a showdown between the military and the Muslim Brotherhood as the electoral commission delayed announcing the winner of a presidential poll claimed by the Islamists.A delay in announcing the results from the run-off, which had been due on Thursday, heightened Brotherhood fears of a "soft coup" by the ruling military, which has already disbanded the Islamist-led parliament and granted itself sweeping powers.A senior Brotherhood official warned the ruling Supreme Council of the Armed Forces (SCAF) that it risked a "confrontation" with the people if Hosni Mubarak's last premier Ahmed Shafiq was declared the winner over Mohamed Morsi.Another Brotherhood leader, Khairat El-Shater, said Islamist supporters would rally "peacefully" if Shafiq was declared the winner, because the Brotherhood had evidence that Morsi won, the group's website reported.Returning officers had handed stamped results to representatives of the rival candidates after completing their tallies, which Morsi's campaign has made public. But only the electoral commission can declare the official result.The commission said results could be announced "on Saturday or on Sunday," the official MENA news agency reported.The results had been expected on Thursday but the commission had said it was delaying the announcement as it studied allegations of fraud from both candidates that might affect the final outcome of the June 16-17 run-off.Shafiq's campaign team, which insists he won despite the Brotherhood claims of victory within hours of polls closing, accuses the Morsi camp of printing almost a million false ballots, the state-owned Al-Ahram newspaper reported.Morsi's campaign denies the allegation and accuses Shafiq's team of bribing voters.The newspaper of the Brotherhood's political arm, the Freedom and Justice Party (FJP), ran a large red banner on its Thursday edition saying: "Sit-in," above an announcement of an open-ended protest until Morsi is sworn in.The military has pledged to transfer power to the winner by the end of the month, but Brotherhood members who set up tents in Cairo's Tahrir Square, the hub of protests that overthrew Mubarak last year, say they are not convinced.They cite the military's assumption of legislative powers after a court ordered parliament dissolved, and decrees giving the army powers of arrest and a broad say in government policy.US Secretary of State Hillary Clinton said on Wednesday it was "imperative" that the military follow through on its promise of a swift handover to civilian rule.Some of the actions by the military leadership in recent days were "clearly troubling," said Clinton, whose government gives Egypt more than one billion dollars a year, mostly in military aid.The generals say they have no intention of remaining in power after a civilian president takes office for the first time since the February 11, 2011 overthrow of Mubarak.The ousted strongman is currently in a coma in a military hospital after suffering a stroke that prompted his transfer from a Cairo prison where he was serving a life sentence, military and medical sources said."This is a constitutional coup," said Brotherhood member Abdel Rahman al-Saoudi, a protester camped out in Tahrir on Thursday morning, adding that he would not leave the square until Morsi's inauguration.The protesters are also demanding that the military repeal an updated interim constitution that allows it to assume parliament's powers and gives it a say in drafting Egypt's next constitution.The sit-in comes after the Brotherhood held a large rally in Tahrir Square on Tuesday."We insist on remaining in the square until we achieve the goals of the revolution and the demands of (the rally) - confronting the military coup against legitimacy," the FJP website quoted senior leader Essam al-Erian as saying.It also quoted Mahmud Ghozlan, a member of the Brotherhood's politburo, as warning there could be "a confrontation between the military and the people," should Shafiq be announced the election winner."The insistence by Shafiq's campaign that he won indicates bad intentions from the military council and the electoral commission," Ghozlan said.Human Rights Watch said military decrees issued over the past month cast doubt on the genuineness of repeated pledges to hand over power."These decrees are the latest indication yet that there won't be a meaningful handover to civilian rule on June 30," the New York-based watchdog's Middle East director Joe Stork said.