Rival protesters have clashed outside the presidential palace in the Egyptian capital, Cairo, as unrest grows over a controversial draft constitution.
Stones were thrown and supporters of President Mohamed Morsi dismantled tents set up by anti-Morsi protesters.
Vice President Mahmoud Mekki has said a referendum on the draft will go ahead on 15 December despite the unrest.
But he indicated that changes could be made after the vote, saying the “door for dialogue” remained open,according to BBC and Reuters.
He urged critics of the draft document to put their concerns in writing for future discussion.
The critics say the draft was rushed through parliament without proper consultation and that it does not do enough to protect political and religious freedoms and the rights of women.
The draft added to the anger generated by Morsi passing a decree in late November which granted him wide-ranging new powers.
In a news conference broadcast live on state television, Mekki said there was “real political will to pass the current period and respond to the demands of the public”.
But he said there “must be consensus” on the constitution, and that “the door for dialogue is open for those who object to the draft”.
“I am completely confident that if not in the coming hours, in the next few days we will reach a breakthrough in the crisis and consensus,” he said.
He stressed his proposal that the opposition put their concerns about particular parts of the constitution into writing was “not a formal initiative but a personal idea”.
Opposition leader Amr Moussa told Reuters he was in discussion with other politicians, but that he wanted to receive a formal request for dialogue from the president.
“We are ready when there is something formal, something expressed in definite terms; we will not ignore it, especially if there is something useful,” he said.
It has spoken about the need for dialogue for some time but has offered few concessions which would end the crisis, he adds.
On Tuesday, tens of thousands of anti-Morsi demonstrators besieged the palace, clashing with police who fired tear gas.
Eighteen people were slightly injured in the brief burst of violence, the official Mena news agency reported.
At one point, the security forces issued a televised statement saying President Morsi had left the building.
Many of those gathered outside the palace, in the suburb of Heliopolis, chanted slogans similar to those directed against the regime of former President Hosni Mubarak during the uprising in February 2011.
President Morsi adopted sweeping new powers in a decree on 22 November, and stripped the judiciary of any power to challenge his decisions.
M.D