By Heba Saleh
BBC News, Cairo
An Egyptian opposition group has urged parliament to reject a constitutional amendment allowing rival candidates to run for president for the first time.
Mr Akef says the amendment is empty of substance
The Muslim Brotherhood and other opposition groups say the amendment has conditions that would exclude anyone outside the ruling party from running.
Parliament's upper house has approved the guidelines and the lower chamber is due to consider them on Tuesday.
The Brotherhood say police are still holding 2,000 of their supporters.
Egyptian President Hosni Mubarak's announcement in February that the constitution would be changed to allow contested presidential elections was hailed as a reform.
But now the opposition says only government candidates could meet the conditions set in the proposed amendment.
Brotherhood leader Mohammed Mehdi Akef urged the lower chamber to reject the proposal when it goes before them on Tuesday.
He said the amendment had been drafted in a way which emptied it of all substance.
Show of force
Mr Akef's comments come at a time of rising confrontation between the government and the Brotherhood, which - although banned as a political party - is represented in parliament by independents.
Thousands of Brotherhood supporters demonstrated across the country in favour of political reform last week.
Islamists are among several groups campaigning against Mubarak
Mr Akef said the authorities arrested some 2,000 of his movement's supporters at the protests.
He said the police used excessive force which led to the death of one demonstrator.
The coordinated protests in several towns were the first time in decades that the Brotherhood had mounted such a blatant show of force.
The movement usually avoids direct confrontations with the authorities, who in turn tolerate some of its activities.
But now that much smaller opposition groups are campaigning openly against another term for Mr Mubarak, it is clear the Brotherhood feels under some pressure to act.
Mr Akef, however, said they would still take measured steps to avoid a head-on collision with the government.