The deputy leader of a rebel mosque in the Pakistani capital, Islamabad, has said he and hundreds of his militant followers are ready to surrender.
Ghazi Abdul Rashid said they would lay down their arms if the security forces ceased firing and did not arrest them.
But the conditions were dismissed by Pakistani government ministers.
The offer to end the confrontation, in which 19 people have died, came after troops pounded the Red Mosque complex, breaching its wall in three places.
Earlier, there were two large explosions near the mosque and the attached religious school.
Security officials said the blasts were probably caused by mortars belonging to the students going off by mistake.
Both sides exchanged fire throughout the day, although the clashes have now stopped.
On Thursday evening much of the city was plunged into darkness, after storms caused failures in the power supply.
Speaking in a telephone interview broadcast on Pakistani television, Abdul Rashid said he had told government mediator Chaudry Shujaat Hussain that his followers were ready to surrender.
"I am making this offer to save the lives of the students," he said.
But Abdul Rashid said he had insisted the authorities promise not to detain anyone who they could not prove belonged to any banned militant groups, or were not wanted for any crime.
"If they are linked to any banned organisation, it can be verified," he said
"It can be looked into... those who are not should be let go."
Abdul Rashid said there had been a smear campaign to make people believe banned militant groups were operating in the mosque.
The cleric also demanded a guarantee of safety for himself and his family, saying he wanted to remain on the premises with his sick mother until they were able to move elsewhere.
Government officials have expressed scepticism that the cleric will honour his promise. They say he has gone back on his word several times.
His brother, the head of the mosque, Maulana Abdul Aziz, earlier urged the militant students to surrender or flee.
Abdul Aziz, who was caught trying to leave the mosque in a burqa on Wednesday, said he realised people inside the mosque could not hold out for long.
"After coming out I saw the siege was massive and came to the conclusion that we should give up," he said.
"I have told them not to sacrifice their lives for me."
The Pakistani government rejected Abdul Rashid's conditional offer to surrender and said the students would be taken into custody.
Deputy Information Minister Tariq Azim Khan said Abdul Rashid and the remaining students would have to lay down their arms unconditionally like all those who left the mosque over the past two days.
"He should allow everybody, women, children to come out. He can come out with them... nobody is going to fire on them," he told Reuters.
"He should surrender himself... If there are cases against him, let the court decide."
The minister said Abdul Rashid was involved in a number of criminal cases.
Earlier, Mr Khan accused the red Mosque Islamists of using women and children as human shields.
"A large number of women and children are being held hostage by armed men in room," he told a press conference.
The interior minister, Aftab Sherpao, said 740 men and 400 women had so far left the mosque.
Mr Sherpao said he believed 300-400 students were still inside, of whom around 50-60 were hardcore militants.
The clerics and their followers have been campaigning for Islamic Sharia law in Islamabad.
Pakistani troops have restricted access to the mosque buildings
Students have kidnapped police officers and people they accuse of involvement in "immoral" acts such as prostitution.
Pakistani President Gen Pervez Musharraf has long been criticised for failing to clamp down on the mosque's activities.
The latest confrontation reportedly started when security forces tried to place barriers around its compound.
On Tuesday, women students of one of two colleges attached to the mosque protested in the street, while their male counterparts traded gunfire with security forces.
The violence took the stand-off to a new level, leaving the authorities little choice but to bring the situation to a conclusion, correspondents say.
The BBC's Barbara Plett in Islamabad says the radicals do not have much support in the capital and people are quite glad to see the government taking them on.
But the authorities' action is likely to upset people in the more conservative North-West Frontier province, where most of the students come from.