Rebels in eastern Libya have said they will not negotiate unless Col Muammar Gaddafi quits and goes into exile.
The National Libyan Council in the city of Benghazi also called again for foreign intervention to stop government air raids against the rebels.The International Criminal Court meanwhile said it would investigate Col Gaddafi and some of his sons for crimes against humanity.
US President Barack Obama repeated his demand that the embattled ruler resign.
In Benghazi, the opposition National Libyan Council said there was no room for talks, following reports that Col Gaddafi had ordered an intelligence chief to negotiate with the rebels.
'Stalemate' The council is led by former Libyan Interior Minister Mustafa Abdel-Jalil, who defected last month.
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End Quote Barack Obama US PresidentMuammar Gaddafi has lost legitimacy to lead and he must leave”
"If there is any negotiation it will be on one single thing - how Gaddafi is going to leave the country or step down so we can save lives. There is nothing else to negotiate," Ahmed Jabreel, a spokesman for Mr Abdel-Jalil, told Reuters news agency.
The BBC's Kevin Connolly in Benghazi says it appears that neither side has the capacity to move large amounts of manpower or firepower over vast expanses of desert.He says that raises the grim prospect of a military stalemate and a political vacuum after the revolt that began in the east of the country in mid-February.
Meaningful talks would be difficult, says our correspondent, because Col Gaddafi's only aim is to remain in power and the rebels' goal is to end his 41 years of rule.
Terror in Tripoli At the beleaguered ruler's stronghold in the capital Tripoli, some residents have called for new protests to be held on Friday after weekly Muslim prayers.
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But there's no doubt that the drivers who are coming through are scared of the wide open roads here. Beyond us, a good 50 miles to the west, lies the much bigger town of Ras Lanouf, with a port, an airfield and an oil refinery.
This is where Col Gaddafi's troops were driven back to after the battle at Brega. If the rebels were a trained army - but they aren't - they would probably want to press their advantage and attack Ras Lanouf.
The line of command is very vague and when we were in Brega earlier this morning, the colonel there was mostly concerned with rescuing two prisoners, supposedly mercenaries, from being lynched by his own men.
At the scene
This is the front line in a strange, desultory war. A checkpoint has been set up in the desert seven miles (11km) beyond the little town of Agayla and manned by no more than a couple of dozen lightly armed rebel soldiers.But there's no doubt that the drivers who are coming through are scared of the wide open roads here. Beyond us, a good 50 miles to the west, lies the much bigger town of Ras Lanouf, with a port, an airfield and an oil refinery.
This is where Col Gaddafi's troops were driven back to after the battle at Brega. If the rebels were a trained army - but they aren't - they would probably want to press their advantage and attack Ras Lanouf.
The line of command is very vague and when we were in Brega earlier this morning, the colonel there was mostly concerned with rescuing two prisoners, supposedly mercenaries, from being lynched by his own men.
Col Gaddafi's security forces have reportedly carried out a wave of arrests, killings and disappearances in the city in recent days.
Meanwhile, US President Barack Obama repeatedly called on Col Gaddafi to quit during a White House news conference on Thursday."Going forward, we will continue to send a clear message: the violence must stop," he said. "Muammar Gaddafi has lost legitimacy to lead and he must leave."
The president also announced he has authorised the use of US military aircraft to help repatriate tens of thousands of migrant workers.
Some 200,000 migrant workers have now fled Libya, into Egypt, Tunisia and Niger, says the International Organization for Migration.
Asked whether he supported a no-fly zone being established over Libya - a key demand of the opposition - Mr Obama said he was examining all options.
The rebels, a mixture of citizen militias and army defectors, have been securing the key port of Brega, home to the country's second largest oil facility.
The government launched a new air strike on Thursday at Brega, but missed its oil refinery target and no casualties were reported.
'More mercenaries' Amid reports that Col Gaddafi has recruited several hundred mercenaries from Mali, opposition forces in Brega are bracing for any fresh ground attacks.
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Luis Moreno-Ocampo: "We cannot confirm the bombing of civilians by planes"
The rebels, armed with machine guns and rocket-propelled grenades, have been holding funerals for some of the 14 fighters killed in Wednesday's battle.
The major western rebel-held cities of Zawiya and Misrata have also repelled attacks by Gaddafi loyalists.
Luis Moreno-Ocampo, chief prosecutor of the International Criminal Court, said Col Gaddafi and his inner circle were under its spotlight.
The court has identified at least nine incidents that could constitute crimes against humanity, including the alleged killing of 257 people in Benghazi last month.
"During the coming weeks, the office will investigate who are the most responsible for the most serious incidents, for the most serious crimes committed in Libya," he said.
Libyan government spokesman Moussa Ibrahim told the BBC the case was "close to a joke", built purely on media reports.
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