Egyptian Isalmist President Mohamed Morsi called for a Dec. 15 referendum on a controversial new constitution Saturday; a day after an Islamist-dominated assembly rushed its passage and as his supporters jammed the streets in a massive demonstration organized by the Muslim Brotherhood.

In a speech Saturday to the constitution-writing assembly that liberal and other ­non-Islamist members had abandoned in protest, Morsi called for a “serious national dialogue” to resolve the political crisis sparked late last month when he decreed that he had near-absolute power in the name of speeding up Egypt’s democratic transition. Morsi has said his decree would be nullified once the constitution is adopted.

“In building our great nation, we have to overcome disagreements to move to build a great future,” Morsi said in his address. “Take into consideration that there are challenges for us in the future at home and abroad. We are capable as Egyptian people.”

However, leading opposition figure Mohamed ElBaradei tweeted that “Morsi put to referendum a draft constitution that undermines basic freedoms and violates universal values…The struggle will continue.”

In his address, Morsi sought to cast the constitution-drafting process as inclusive, despite the walkouts by secular, liberal, Christian and other non-Islamist members who felt thwarted by the Islamist majority. It is a document, he said, in which “the people are the source of authority.”

But Morsi’s decree, the hasty vote on the charter and now his decision to follow through with the public vote to approve it seem likely only to further galvanize Egypt’s normally fragmented opposition, which has already drawn improbable support from judges and other former Mubarak-era figures. Protesters have hit the streets by the tens of thousands over the past eight days, some calling for Morsi’s ouster, fearful he is becoming an Islamist version of Mubarak, but most urging him to abandon his decree and start the process of drafting the constitution all over again.

However on Saturday, Morsi, who has voiced suspicion that the opposition is being hijacked by Mubarak loyalists, dismissed the idea of writing a new draft of the constitution. “Egyptians are adamant about going forward to reach the objectives of the blessed revolution,” he said.

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