By Tamim Elyan
CAIRO, June 18 (Reuters) - Members of Egypt's constituent assembly vowed to hold their first meeting at the parliament building on Monday in a show of defiance against the army's assumption of legislative powers.
The assembly is due to write a new constitution as part of a transition to democracy engineered by the generals who took power after the overthrow of President Hosni Mubarak's autocratic government last year.
But that transition was thrown into disarray last week when a court of Mubarak-era judges ruled that the parliamentary election was invalid and the chamber must be dissolved.
On Sunday, the ruling military council issued a decree allowing it to write laws and to name a new constituent assembly if necessary, prompting some analysts to say the generals were insuring themselves against a possible Islamist win when presidential election results are announced on Thursday.
Islamists and liberals united to denounce a "military coup" and parliamentary speaker Saad al-Katatni said parliament could only be rendered void by popular referendum.
"We will meet, even if it is on the pavement, unless they use snipers against us," said liberal MP Mohamed el-Sawy, one of the 100 people appointed by parliament to write the democratic constitution.
"We are holding on to this constituent assembly. It is the only gain we took away from the legitimate parliament."
Employees of parliament were under orders to block entry to the building in Cairo after the assembly was declared void last week, members of the defunct parliament said.
Officially, the constitution writing process is unaffected by the removal of parliament.
But the army's decree gives it the right to form a new constitution-writing body if the current one "encounters any obstacles in completing its role" and to oppose any article that contradicts the "goals of the revolution".
"The army will try to use the first opportunity to get rid of it and form a new assembly," said Gamal Abdel Gawad, politics professor at the American University in Cairo.
Analysts say the army might be seeking to secure a special status in the next constitution to protect the economic interests and prestige it has maintained since a 1952 revolution against the monarchy.
The constituent assembly - comprising members of parliament and representatives of professional, labour and other interest groups - planned to choose a head and two deputies on Monday. Sawy said it would show they were pressing ahead with their work.
The assembly's make-up is itself controversial; most liberals and leftists have withdrawn from it because they say it is biased towards the Islamists who dominated the dissolved parliament, and fails to represent Egypt's diverse social groups fairly.
Islamist Mohamed Morsy and former air force commander Ahmed Shafik both claim to have won the presidential election run-off. (Editing by Tom Pfeiffer and Kevin Liffey)