CAIRO, Egypt -- Egypt's liberal opposition called for more protests Sunday, seeking to keep up the momentum of its street campaign after the president made a partial concession overnight but refused its main demand he rescind a draft constitution going to a referendum on Dec. 15.

President Mohammed Morsi met one of the opposition's demands, annulling his Nov. 22 decrees that gave him near unrestricted powers. But he insisted on going ahead with the referendum on a constitution hurriedly adopted by his Islamist allies during an all-night session late last month.

The opposition National Salvation Front called on supporters to rally against the referendum. The size of Sunday's turnout, especially at Cairo's central Tahrir square and outside the presidential palace in the capital's Heliopolis district, will determine whether Morsi's concession chipped away some of the popular support for the opposition's cause.

The opposition said Morsi's rescinding of his decrees was an empty gesture since the decrees had already achieved their main aim of ensuring the adoption of the draft constitution. The edicts had barred the courts from dissolving the Constituent Assembly that passed the charter and further neutered the judiciary by making Morsi immune from its oversight.

Still, the lifting of the decrees could persuade many judges to drop their two-week strike to protest what their leaders called Morsi's assault on the judiciary. An end to their strike means they would oversee the Dec. 15 vote as is customary in Egypt.

If the referendum goes ahead, the opposition faces a new challenge -- either to campaign for a "no'' vote or to boycott the process altogether. A low turnout or the charter passing by a small margin of victory would cast doubts on the constitution's legitimacy.

It was the decrees that initially sparked the wave of protests against Morsi that has brought tens of thousands into the streets in past weeks. But the rushed passage of the constitution further inflamed those who feel Morsi and his Islamist allies, including the Muslim Brotherhood, are monopolizing power in Egypt and trying to force their agenda.

The draft charter was adopted amid a boycott by liberal and Christian members of the Constituent Assembly. The document would open the door to Egypt's most extensive implementation of Islamic law, enshrining a say for Muslim clerics in legislation, making civil rights subordinate to Shariah and broadly allowing the state to protect ``ethics and morals.'' It fails to outlaw gender discrimination and mainly refers to women in relation to home and family.

Sunday's rallies would be the latest of a series by opponents and supporters of Morsi, who hails from the Muslim Brotherhood.

Both sides have drawn tens of thousands of people into the streets, sparking bouts of street battles that have left at least six people dead and hundreds wounded. Several offices of the Muslim Brotherhood also have been ransacked or torched in the unrest.

Morsi, who took office in June as Egypt's first freely elected president, rescinded the Nov. 22 decrees at the recommendation Saturday of a panel of 54 politicians and clerics who took part in a ``national dialogue'' the president called for to resolve the crisis. Most of the 54 were Islamists who support the president, since the opposition boycotted the dialogue.

Bassem Sabry, a writer and activist, called the partial concession a "stunt'' that would embarrass the opposition by making it look like Morsi was willing to compromise but not solve the problem.

"In the end, Morsi got everything he wanted,'' he said, pointing out the referendum would be held without the consensus Morsi had promised to seek and without giving people sufficient time to study the document.

In his overnight announcement, Morsi also declared that if the draft constitution is rejected by voters in the referendum, a nationwide election would be held to select the next Constituent Assembly.

The assembly that adopted the draft was created by parliament, which was dominated by the Brotherhood and other Islamists, and had an Islamist majority from the start. The lawmaking lower house of parliament was later disbanded by court order before Morsi's inauguration.

If the draft is approved in the referendum, elections would be held for a new lower house of parliament would be held within two months, Morsi decided.

The deepening political rift in Egypt had triggered a warning Saturday from the military of ``disastrous consequences'' if the constitutional crisis isn't resolved through dialogue.

"Anything other than (dialogue) will force us into a dark tunnel with disastrous consequences, something which we won't allow,'' the military said in a statement broadcast on state TV and attributed to an unnamed military official.

It was the first political statement by the military since the newly elected Morsi sidelined it from political life soon after he was sworn in.

With the spectre of more fighting among Egyptians looming, the military sealed off the presidential palace plaza with tanks and barbed wire -- and on Saturday set up a wall of cement blocks around the palace.

Both sides have accused the other of turning the political battle into a violent street clash that could spiral out of control.

Leaders of the Muslim Brotherhood have spoken of a "conspiracy'' hatched by figures of the ousted regime of Hosni Mubarak aimed at ousting Morsi.

Meanwhile, the opposition accused gangs organized by the Brotherhood and other Islamists of attacking its protesters, calling on Morsi to disband them and open an investigation into the bloodshed.

Members of a so-called Alliance of Islamists forces warned it will take all measures to protect ``legitimacy'' and the president -- comments that signal further violence may lie ahead.

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  • Egyptian protesters chant slogans at rally in Tahrir Square in Cairo, Egypt, Tuesday, Nov. 27, 2012. Egyptians flocked to Cairo's central Tahrir square on Tuesday for a protest against Egypt's president in a significant test of whether the opposition can rally the street behind it in a confrontation aimed at forcing the Islamist leader to rescind decrees that granted him near absolute powers. (AP Photo/ Khalil Hamra)

  • Egyptian protesters attend an opposition rally in Tahrir Square in Cairo, Egypt, Tuesday, Nov. 27, 2012. Thousands flocked to Cairo's central Tahrir square on Tuesday for a protest against Egypt's president in a significant test of whether the opposition can rally the street behind it in a confrontation aimed at forcing the Islamist leader to rescind decrees that granted him near absolute powers.(AP Photo/Khalil Hamra)

  • A masked Egyptian protester takes cover during clashes with security forces near Tahrir square, where an opposition rally has been called for to voice rejection of President Morsi's seizure of near absolute powers, in Cairo, Egypt, Tuesday, Nov. 27, 2012. Egyptian protesters and police clashed in Cairo on Tuesday just hours ahead of a planned massive rally by opponents of the country's Islamist president demanding he rescind decrees that granted him near-absolute powers.(AP Photo/ Khalil Hamra)

  • Tens of thousands people take part in a mass rally against a decree by President Mohamed Morsi granting himself broad powers on November 27, 2012 at Egypt's landmark Tahir Square in Cairo. Clashes between police and protesting youths erupted near Cairo's Tahrir Square, ahead of the demonstration. The planned demonstrations come a day after Morsi stuck by his controversial decree in a meeting with judges that was aimed at defusing the worst political crisis since his election in June. (GIANLUIGI GUERCIA/AFP/Getty Images)

  • An Egyptian protester attempts to throw back a tear gas canister on November 27, 2012 during clashes with the Egyptian Riot Police in Omar Makram street, off Tahrir Square in Cairo. Clashes between police and protesting youths erupted on Tuesday near Cairo's Tahrir Square, ahead of a mass rally against a decree by President Mohamed Morsi granting himself broad powers. The planned demonstrations come a day after Morsi stuck by his controversial decree in a meeting with judges that was aimed at defusing the worst political crisis since his election in June. (GIANLUIGI GUERCIA/AFP/Getty Images)

  • An Egyptian protester blows a stadium horn as he gestures at a cordon of security forces near Tahrir square, where an opposition rally has been called for to voice rejection of President Morsi's seizure of near absolute powers, in Cairo, Egypt, Tuesday, Nov. 27, 2012. Egyptian protesters and police clashed in Cairo on Tuesday just hours ahead of a planned massive rally by opponents of the country’s Islamist president demanding he rescinds decrees that granted him near-absolute powers. (AP Photo/ Khalil Hamra)

  • Egyptian security forces arrest a protester during clashes near Tahrir square in Cairo, Egypt, Tuesday, Nov. 27, 2012. Egyptian protesters and police clashed in Cairo on Tuesday just hours ahead of a planned massive rally by opponents of the country’s Islamist president demanding he rescinds decrees that granted him near-absolute powers.(AP Photo/ Khalil Hamra)

  • An Egyptian protester hurls a stone during clashes with security forces, unseen, in Cairo, Egypt, Wednesday, Nov. 21, 2012. Egyptian protesters firebombed one of the offices of satellite broadcaster Al-Jazeera on Wednesday and attacked a police chief who tried to negotiate an end to three days of violent protests in central Cairo.(AP Photo/Ahmed Gomaa)

  • An Egyptian protester drags a security barrier during clashes outside the country's high court in Cairo, Egypt, Saturday, Nov. 24, 2012. Egypt’s highest body of judges slammed on Saturday a recent decision by the president to grant himself near-absolute power, calling the move an “unprecedented assault” on the judiciary. The statement from the Supreme Judicial Council came as hundreds of demonstrators clashed with police outside a downtown Cairo courthouse. They were protesting the Thursday declaration by President Mohammed Morsi that courts could not overrule his decrees until a new constitution and parliament is in place, several months if not more in the future. (AP Photo/Mohammed Asad)

  • Egyptian protesters gather outside the country's high court in Cairo, Egypt, Saturday, Nov. 24, 2012. Egypt’s highest body of judges slammed on Saturday a recent decision by the president to grant himself near-absolute power, calling the move an “unprecedented assault” on the judiciary. The statement from the Supreme Judicial Council came as hundreds of demonstrators clashed with police outside a downtown Cairo courthouse. They were protesting the Thursday declaration by President Mohammed Morsi that courts could not overrule his decrees until a new constitution and parliament is in place, several months if not more in the future. (AP Photo/Mohammed Asad)

  • Egyptian protesters gather in Tahrir Square in Cairo, Egypt, Sunday, Nov. 25, 2012. President Mohammed Morsi edicts, which were announced on Thursday, place him above oversight of any kind, including that of the courts. The move has thrown Egypt's already troubled transition to democracy into further turmoil, sparking angry protests across the country to demand the decrees be immediately rescinded. The banner in Arabic, top center, reads, "members of the Muslim Brotherhood are not allowed." (AP Photo/Ahmed Gomaa)

  • An Egyptian protester shouts political slogans against President Mohamed Morsi's decree granting himself broad powers as others wave their national flag during a demonstration in Cairo's Tahrir Square on November 27, 2012. The planned demonstrations come a day after Morsi met with the country's top judges in a bid to defuse the crisis over the decree, that has sparked deadly clashes and prompted judges and journalists to call for strike. (GIANLUIGI GUERCIA/AFP/Getty Images)

  • An Egyptian protester recovers from tear gas inhalation on November 27, 2012, during clashes with the Egyptian Riot Police in Omar Makram street, off Tahrir Square in Cairo. Clashes between police and protesting youths erupted near Cairo's Tahrir Square, ahead of a mass rally against a decree by President Mohamed Morsi granting himself broad powers. The planned demonstrations come a day after Morsi stuck by his controversial decree in a meeting with judges that was aimed at defusing the worst political crisis since his election in June. (GIANLUIGI GUERCIA/AFP/Getty Images)

  • A group of protesters shout slogans against Egypt's President Mohammed Morsi during a demonstration in front of the White House in Washington on November 26, 2012. Morsi stuck by a controversial decree granting him sweeping powers, on the eve of planned nationwide rallies to protest the move, in the worst crisis since his election in June. (JEWEL SAMAD/AFP/Getty Images)

  • A group of protesters shout slogans against Egypt's President Mohammed Morsi during a demonstration in front of the White House in Washington on November 26, 2012. Morsi stuck by a controversial decree granting him sweeping powers, on the eve of planned nationwide rallies to protest the move, in the worst crisis since his election in June. (JEWEL SAMAD/AFP/Getty Images)