CAIRO - Egyptian President Mohammed Morsi called Saturday for a Dec. 15 referendum on a new constitution, 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.

Morsi called for a "serious national dialogue" to resolve the political crisis sparked last week when he decreed himself 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," he said. "We are capable as Egyptian people."

In the streets around Cairo University, tens of thousands of moderate and more conservative Islamists -- the same ones who had joined the revolution that ousted strongman Hosni Mubarak nearly two years ago -- cheered and waved Egyptian flags as Morsi announced a referendum they see as a moment of national triumph.

The other revolutionaries -- members of the liberal and more secular segments of society who have been protesting against Morsi's move all week -- see it as a step away from their vision of a progressive Egypt.

"Morsi put to referendum a draft constitution that undermines basic freedoms and violates universal values," tweeted Mohamed ElBaradei, the leading liberal opposition figure.

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. Morsi's decree, the hasty vote on the charter and now his decision for a public vote to approve it seem likely only to further galvanize the normally fragmented opposition. "He is calling for national dialogue? What dialogue? I mean, he refused dialogue," said Amro Suleiman, an official with the liberal Free Egyptians Party. "We feel the whole thing has been cooked. It is difficult to say what the reaction will be, but it will not be quiet."