Fresh protests are taking place in Cairo, a day after Egyptian President Mohamed Morsi pledged to forge on with a controversial constitutional referendum and condemned street violence that has gripped the nation's capital.
Morsi's offer in an overnight address for dialogue to resolve the crisis, prompted by his November 22 decree giving himself supreme powers, was rejected by opposition groups on Friday.
The National Salvation Front, the main opposition group, said that it was not taking part in the dialogue.
Mohamed ElBaradei, a prominent opposition leader whose party is a member of the NSF, also urged political forces to shun the dialogue process. The liberal Wafd party added its voice to that call.
In his address overnight, Morsi had proposed a meeting on Saturday with political leaders, "revolutionary youth" and legal figures to discuss the way forward.
He called the recent violence "regrettable", and blamed it on "infiltrators" funded by unnamed third parties.
"Such painful events happened because of political differences that should be resolved through dialogue," he said.
In response, opposition groups have said they would step up their campaign against the decree and the referendum set for December 15.
Protests were expected to swell after traditional Muslim prayers on Friday.
Crisis 'building up'
Gamal Abdel Gawad, a political analyst, told Al Jazeera on Friday that the crisis was continuing to build up.
"The presidential speech did not provide any serious way out," he said.
"There will be large protests today, and in the coming days. The call for dialogue will not be enough to defuse this crisis.
"There will be some sort of a showdown between the Muslim Brotherhood and the opposition."
In his speech on Thursday night, Morsi said the referendum on the constitution would go ahead as planned, adding that "afterwards ... everyone must follow its will".
He said: "We respect peaceful freedom of speech but I will never allow anyone to resort to killing and sabotage."
The opposition coalition, the National Salvation Front, issued a statement saying "the fact that the presidency ... persists in ignoring the demands and protests of the people has closed the door on any attempt for dialogue".
It said it "renews its call for Egyptians to gather across Egypt on Friday".
The group's spokesman, Hussein Abdel Ghani, said "we will continue to escalate [protests], using peaceful means".
A youth opposition group in the coalition, April 6, called for marches from all of Cairo's mosques to converge on the main squares.
There were fears of more violence after clashes in Egypt on Wednesday between pro- and anti-Morsi protesters that left seven people dead and more than 600 injured.
The army on Thursday cleared the area in front of the presidential palace in the capital of protesters from both sides, and deployed tanks and barbed wire to keep crowds away.
The demonstrations were the biggest since Morsi's election in June. The street clashes were also reminiscent of the upheaval in February 2011 that ended Hosni Mubarak's presidency.
At least four of Morsi's advisers have quit over the crisis, and the Cairo stock market has taken a heavy hit from the latest violence.
US President Barack Obama expressed "deep concern" on Thursday over the events in Egypt, in a call to Morsi, the White House said.
Obama also told Morsi that it was "essential for Egyptian leaders across the political spectrum to put aside their differences and come together to agree on a path that will move Egypt forward," the White House said in a statement.