The text of Egypt's new constitution was set to be completed on Wednesday and voted on the following morning, with the controversial document the focus of of a legal and ideological battle.
"The discussions over the draft of the constitution will be finished today, to be followed by voting," Ahmed Darrag, the secretary general of the constituent assembly said in remarks carried by the official MENA news agency.
The news agency said the panel would vote on the draft on Thursday morning. It would later be put to a referendum.
The head of the Islamist-dominated panel, Hossam al-Gheriani, urged the liberal, leftist and Coptic members who walked out to "come back and finish the discussion on Thursday."
"Tomorrow will be a great day," Gheriani said.
The surprise move comes as the country is deeply divided over the constituent assembly which critics have slammed for failing to represent all Egyptians.
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Anger over the document was exacerbated following a decree by President Mohamed Morsi granting himself sweeping powers and barring the courts from dissolving the panel.
The Supreme Constitutional Court had been due to review the legality of the drafting committee on Sunday, but its fate hangs in the balance amid the constitutional vacuum.
The court said on Wednesday that it would go ahead with its session on Sunday, although Morsi's decree stripped it of the power to make a ruling on the panel.
Human rights groups have criticised the move to rush through the constitution.
"This is not a healthy moment to be pushing through a constitution because this is an extremely divisive moment," Human Rights Watch Egypt director Heba Morayef told AFP.
"Human rights groups have very serious concerns about some of the rights protections in the latest drafts we've seen," she said.
Liberals and representatives of Egypt's churches had already withdrawn from the panel, complaining that it was undemocratic and rushed.
The new constitution is to replace the 1971 charter suspended by the military which took power when president Hosni Mubarak was ousted in February last year.