Protests by the president's supporters have prevented Egypt's Supreme Constitutional Court from meeting in Cairo for a key ruling on a draft constitution, state media say.Hundreds of protesters are trying to block any attempt to dissolve the panel that passed the draft.President Mohammed Morsi has tried to bypass the court by assuming new powers and speeding through the draft.His opponents say the document undermines basic freedoms.On Saturday, Mr Morsi called a referendum on the draft constitution for 15 December.Sweeping new powers he adopted in a decree on 22 November stripped the judiciary of any power to challenge his decisions, so it is unclear what effect any Supreme Constitutional Court ruling would have.However, analysts say any ruling opposing his decisions would be a direct challenge and would bolster the opposition campaign to have his decree annulled.'Democratic system'The Egyptian state news agency Mena says demonstrations outside the constitutional court have prevented the judges from getting into the building.It is not clear yet whether they will reconvene elsewhere on Sunday and a statement from the court is expected in the next few hours.The court was also to rule on whether to dissolve the Islamist-dominated upper house of parliament, the Shura Council, although Mr Morsi's decree would also negate such a ruling.The president's supporters rushed the draft thought the constituent assembly on Thursday night.After receiving a copy of the document on Saturday, Mr Morsi called on "all Egyptians" to take part in the referendum, whether or not they agreed with the draft."The world is looking at how Egyptians will build their institutions to establish their democratic system," the president said.His announcement was hailed at a rally in Cairo on Saturday, with the crowds chanting, "The people support the president's decision!"'Struggle will continue'The BBC's Jon Leyne in Cairo says that the two weeks until the ballot will be tense, as Egyptians prepare to vote not just on the constitution but also on the country's future.The draft constitution and the recent decree have prompted widespread protests by opponents.Many anti-government activists remain camped out in Cairo's Tahrir Square."Morsi put to referendum a draft constitution that undermines basic freedoms and violates universal values. The struggle will continue," key opposition figure Mohamed ElBaradei tweeted on Saturday.If approved, the new text will overwrite all constitutional declarations - including Mr Morsi's decree - and a new parliament should be elected within 60 days.Among the historic changes to Egypt's system of government, the draft limits a president to two four-year terms. It also introduces some civilian oversight of the military.The draft keeps in place an article defining "principles of Sharia", or Islamic law, as the main source of legislation.Mr Morsi's supporters point to the fact that he is Egypt's first freely elected president and argue that liberals and secularists do not represent the vast majority of Egyptians.But the extent of Mr Morsi's new powers has raised fears that he might become a new dictator.