Cairo — Egyptian President Mohamed Morsi annulled a decree that granted him expansive power and the army was mobilised to maintain security, officials said. The Egyptian cabinet approved measures permitting the army to use force if "necessary to perform their duty," al-Ahram newspaper reported.

The concession offered by Morsi failed to placate opponents who accused him on Sunday of plunging Egypt deeper into crisis by refusing to postpone a vote on a constitution shaped by Islamists.

Islamists say they see the referendum as sealing a democratic transition that began when a popular uprising toppled Hosni Mubarak 22 months ago after three decades of military-backed one-man rule.

Their liberal, leftist and Christian adversaries say the document being fast-tracked to a vote could threaten freedoms and fails to embrace the diversity of Egypt's 83 million people.

Islamist politician Mohammed Selim el-Awa told a news conference Saturday the referendum on a draft constitution on Dec.15 would go ahead as planned and be immune from judicial appeal, al-Masry al-Youm said.

"If the people voted no to the referendum, a new Constituent Assembly will be formed within three months via general elections, after which it will write a new constitution within six months," he said

However, one of the key demands of Morsi's opponents was to halt the referendum. Ahmed Said, head of the Free Egyptians Party and a key member of the National Salvation Front coalition, called Morsi's announcement shocking, saying it failed to halt the referendum.

Former presidential candidate Mohamed ElBaradei, one of the founders of the National Salvation Front, called Morsi's decision " arm-twisting."