Cairo, Egypt (CNN) -- Egypt's top political parties have agreed to nominate a member of the Muslim Brotherhood as the nation's next parliament speaker, the first time in decades that an Islamist would hold that post.
The Brotherhood's Freedom and Justice Party won more than 40% of the seats in recent elections and is expected to lead the country's first parliament chosen since the ouster of former President Hosni Mubarak.
The FJP-led alliance nominated its secretary-general, Mohamed al-Katatni, as parliament speaker.
Al-Katatni, described as a moderate on the Brotherhood's website, was detained by Mubarak's state security forces together with FJP leaders Essam El-Erian and Mohamed Morsi, the chairman of the FJP.
The parliament, which will be seated later this month, must appoint a 100-member panel to write a new Egyptian constitution. Presidential elections are set for June.
Liberals fear that electoral gains for Islamists will steer Egypt down a rigid path away from democracy.
Morsi tried to reassure Egyptians that the new constitution "will be drafted without exemption of any stakeholders or exclusion of any parties, forces or currents."
"We continue the march of the peaceful revolution, the Egyptian revolution of January 25, which has achieved some of its objectives and as yet continues to achieve remaining ones," he said. "There is no doubt that the parliamentary election results were expressive of all Egyptians and their free will, the new parliament, too."
The agreement, signed Monday by six leading political parties, also allows the hardline Al Nour party and the liberal Al Wafd party to nominate two deputy speakers.
But Al Wafd was not present at the meeting and did not sign the agreement.
"We were not informed of about the meeting and will announce our decision after our board meeting on Thursday," Bahaa Abu Shaka, Al Wafd's deputy chief, told CNN.
The new parliament convenes a year after popular revolts erupted, eventually leading to Mubarak's downfall.
The longtime dictator is on trial on charges of corruption and ordering the deaths of hundreds of protesters.
The Supreme Council of the Armed Forces has led Egypt's government since Mubarak's fall. It has said it will hand over power to a new government once one is in place.
But the transition has not been quick or transparent enough for some Egyptians. A series of protests in Cairo last month resulted in violent and sometimes deadly clashes between demonstrators and soldiers.
Gen. Mohamed Hussein Tantawi, who heads the Supreme Council, is expected to address the new parliament, according to the Morals Affairs Military Department.