By Yasmine Saleh and Dina Zayed
CAIRO (Reuters) - Egyptian lawmakers held a heated debate on Saturday as they began selecting 100 people tasked with writing a new constitution, a process crucial to future democracy in the country after the ouster of Hosni Mubarak.
The document will define the balance of power between the army-backed executive and parliament, which wants to curb broad presidential powers and may become the focus of confrontations over the role of Islam in Egyptian laws and society.
The constitution will also outline the future political role of the military, which has been in power since the autocratic Mubarak was toppled in a popular uprising in February 2011.
Under an interim constitution, parliament is responsible for picking the 100-strong assembly that will write the new constitution, replacing the one that helped keep Mubarak in power for three decades and was a cornerstone of his rule.
"The most important step to building democratic institutions is what we are about to do here today," Saad al-Katatni, the speaker of the lower house of parliament, said at the start of a joint session between the two houses.
"The path of our revolution was not paved with flowers but with sacrifices," he said after asking lawmakers to read a verse of the Quran in honor of the victims of the uprising.
As members of parliament in the Arab world's most populous state and long-time U.S. ally outlined their visions for the make-up of the body, early signs of disagreement were evident.
The Muslim Brotherhood's Freedom and Justice Party (FJP), which controls most seats in both houses of parliament combined, wants 40 members of the constituent assembly to be from parliament and the remaining 60 to include legal and constitutional experts and members of unions.
That vision is at odds with that of liberal groups in parliament, who stress that women, youth and Christians get a fair share of the positions in the assembly.
Both the liberals and the Brotherhood's Salafi rivals, which calls for a strict application of Islamic law, worry the FJP will have more say in the drafting of the new constitution.
To counter that risk, the Salafi al-Nour Party wants more lawmakers in the assembly than advocated by the FJP.
"We see that those in a better position to be in the assembly should be the elected members of parliament. They should have a priority over others," said Nour's Moustafa Khalifa.
The FJP insists it wants an assembly that can represent all parties, and a constitution that can safeguard Egypt's freedoms.
"We want an assembly that represents all of Egypt's people and we will cooperate with everyone from inside parliament and outside to do so," said Hussein Ibrahim, an FJP lawmaker.
Once the assembly is put together, it has six months to draft the constitution, which will then be put to a referendum.
But the fierce debate in selecting the assembly members may be a foretaste of the difficulties in writing the document.
Political parties aim to play a significant role in the constitution-writing process, where some hard-line Islamists may seek to impose changes curbing citizens' freedoms.
The assembly will try to establish what role to give to the military, which for decades has had no civilian oversight. Some Islamists are expected to defend the status of the military, while other politicians would resist that.
"The process of granting Egypt a new constitution will not be an easy one. Egyptians need real debate about their constitution," liberal lawmaker Amr Hamzawy told Reuters this week.
Some lawmakers kicking off the process on Saturday stressed that expertise, rather than party affiliation, should be the crucial factor when selecting members of the assembly.
"Picking the constituent assembly should be governed by expertise and not numbers, it should be about caring for substance and not appearances," Essam Sultan, a lawmaker with the moderate Islamist Wasat party, told parliament.
(Additional reporting by Omar Fahmy; Writing by Dina Zayed; Editing by Alessandra Rizzo)