Egypt's army-backed government on Thursday warned supporters of deposed president Mohamed Mursi to abandon their Cairo protest camps, promising them a safe exit if they gave up without a fight.
The appeal, made by Interior Ministry spokesman Hany Abdel Latif on state television, followed the government's declaration on Wednesday it was ready to take action to end two weeks of sit-in protests by thousands of Mursi supporters at two sites.
Since the army ousted the Islamist Mursi on July 3, police have rounded up many leaders of his Muslim Brotherhood, mostly on charges of inciting violence. The latest warnings raised the possibility of a potentially bloody showdown.
Latif said that if protesters left the sites peacefully, they would be guaranteed a safe exit. No deadline was set.
"There is no specified date. We will continue to study the situation on the ground," Latif told Reuters.
The protesters remained defiant on Thursday and prepared for the worst.
At the Rabaa al-Adawiya camp, ground was cleared of rubbish to allow easier ambulance access. Buckets of sand were placed throughout the camp to be used to extinguish tear gas canisters.
Behind a barricade of bricks and sandbags, rocks had been piled up to use as ammunition.
"We are ready. We are ready to die for legitimacy. An attack can happen at any moment," said Mohamed Saqr, a Brotherhood activist guarding an entrance to the encampment at a mosque in northeast Cairo.
Egypt is now more polarized than at any time since the U.S.-backed autocrat Hosni Mubarak was toppled in 2011, starting a political transition fraught with unrest.
Mursi became Egypt's first freely-elected leader in June 2012 but faced opposition over his inability to address social and economic problems and fears that he was leading the country towards stricter Islamist control.
The new government's transition plan envisions parliamentary elections in about six months, to be followed by a presidential vote. The Brotherhood says the army has mounted a coup against a legitimate elected leader and wants nothing to do with the plan.
The government was buoyed by huge pro-army rallies on Friday in response to a call by army chief General Abdel Fattah al-Sisi for Egyptians to give him a mandate to crack down on "violence and terrorism".
Mursi has been in army detention since his overthrow and faces a judicial inquiry into accusations that include murder and kidnapping. The authorities also brought formal charges on Wednesday against the Brotherhood's three top leaders, two of whom are in custody.
The arrests, along with street violence that has killed well over 100 Mursi supporters, have fuelled global concern that the government plans to crush the Brotherhood even though it says it wants to involve the Islamists in the transition plan.
Khaled Hanafi, general secretary of Freedom and Justice Party, the Muslim Brotherhood's political arm, said the interior minister was trying to terrorize the protesters.
"These statements won't deter peaceful protesters and will only increase their determination and resolve to fulfill their demands for a return of legitimacy, and they will not leave the squares until legitimacy returns," he said.
A prominent Salafi cleric, Sheikh Mohamed Hassan, warned the government against spilling blood.
"Egypt's crisis will not be resolved with blood and piles of corpses," he said, urging dialogue and saying anyone who thought it could resolved in "a battle of blood-letting" was deluded.
"The crisis will deepen and the strife will increase. The division will increase. Egypt will never settle down, he said in an address broadcast by Al Jazeera's Egyptian news channel.
Egypt's biggest liberal and leftist coalition, the National Salvation Front, said it supported "all legal measures aimed at restoring security and stability".
The group, which backed Mursi's overthrow, said the authorities should confront what it called a "campaign of incitement and intimidation by the Brotherhood and their allies."
A grouping of Mursi supporters calling itself the Anti-Coup Pro-Democracy Alliance said the security forces planned to foment violence as an excuse for committing a massacre. It appealed to soldiers and police not to fire on protesters.
It said the protests would continue.
"All revolutionary groups, including the Alliance, also announce that they do not recognize the coup government or its decisions or negotiations," it said in a statement.
"They will continue in spite of threats, and will not be made to back down from their right to peaceful protests and sit-ins, regardless of the strength of their opposition."
The prospect of a showdown appeared to undermine efforts by the European Union to negotiate a peaceful settlement.
EU foreign policy chief Catherine Ashton spent two days in Cairo this week and met Mursi when she was flown after dark by military helicopter to his secret place of confinement.
The visiting German foreign minister, Guido Westerwelle, on Thursday urged the authorities to avoid "the appearance of selective justice".
But his Egyptian counterpart, Nabil Fahmy, speaking alongside him, retorted that there was no agenda of vengeance and no selective justice.
"There is law and it applies to everyone," Fahmy said.
Any forcible action against the Mursi supporters could set off more bloodletting after security forces killed 80 Brotherhood followers on Saturday. The Brotherhood has called for a "million-man march" on Friday.
Almost 300 people have been killed in violence since Mursi's overthrow, inspiring fears in the West of a wider conflagration in Egypt, which straddles the Suez Canal and whose 1979 peace treaty with Israel is central to U.S. policy in the Middle East.