CAIRO — Egypt's opposition coalition reaffirmed its rejection of the Dec. 15 referendum on a disputed constitution draft and rallied their supporters for protests in Tahrir Square and in cities across the country on Tuesday, saying in a statement Sunday night that dialogue with President Mohammed Morsi was impossible given the president's decision to hold firm on the referendum date.

A National Salvation Front spokesman read a statement at a news conference, saying the group, which includes Egypt's most prominent opposition figures, was ready for dialogue if the president agreed to cancel the referendum. The coalition also pledged to lead a widespread civil disobedience campaign of strikes by various labor forces that would "paralyze the economy." While they reiterated their stance that they were treating Morsi as the elected president, they also warned that his uncompromising stance was leading the country toward civil war.

The president's move to rescind his Nov. 22 decree — announced around midnight Saturday — did not satisfy the opposition's main demand: the cancellation of the Dec. 15 referendum. Nearly all of the groups protesting what they say is a power grab by Morsi had boycotted the Saturday dialogue meeting convened by the president for the same reason, saying that negotiation was not possible given the president's decision to hold firm on the referendum date.

Also on Saturday, Egypt's military made its first public comment on the political crisis. A statement read by an unnamed military spokesman was interpreted by many as the military's decision to re-insert itself into the political scene for the first time since the president pushed them aside in August, ordering top officers into retirement and canceling the constitutional declaration that had established the country's most powerful institution as the legislative authority after parliament was dissolved before Morsi took office.