US President Barack Obama has called the leaders of the UK, France and Italy as international efforts to respond to the crisis in Libya gather pace.
Mr Obama outlined a range of possible measures, including plans for humanitarian assistance.
Earlier, the White House said all options were on the table, including sanctions. It said the military would present its own proposals to Mr Obama.
Libyan leader Muammar Gaddafi meanwhile blamed the uprising on al-Qaeda.
Speaking on state television, he repeated claims that hallucinogenic drugs had been given to young people to incite them to revolt.
Opposition supporters in Tripoli have said they are planning to protest in Green Square after Friday prayers at noon (1000 GMT).
On Thursday, fierce fighting was reported in nearby towns, as pro-Gaddafi forces tried to regain control of areas seized by the opposition.
A witness in Zawiya, 50km (30 miles) to the west, said an army unit had attacked protesters with machine guns and rocket-propelled grenades.
Ships and military aircraft have been sent to evacuate thousands of foreign nationals trying to flee the turmoil.
'Ruling out nothing'
On Thursday, Mr Obama telephoned French President Nicolas Sarkozy of France, UK Prime Minister David Cameron and Italian Prime Minister Silvio Berlusconi to co-ordinate a response to the Libya crisis.
"The president expressed his deep concern with the Libyan government's use of violence which violates international norms and every standard of human decency," said a statement.
"The leaders discussed the range of options... to hold the Libyan government accountable for its actions, as well as planning for humanitarian assistance."
US officials said the steps could include seeking stronger action by the UN Security Council - including possible sanctions such as travel bans and asset freezes - support for calls to suspend Libya from the UN Human Rights Council, and enforcing a no-fly zone over Libya.
When asked earlier whether the US was considering military action, White House spokesman Jay Carney said he could not rule out "bilateral options".
The UN Security Council is expected to meet later on Friday in New York to consider further action against Col Gaddafi's government.
The UK's permanent representative, Mark Lyall Grant, had told the Council's 15 member states at a closed session on Thursday that Col Gaddafi had failed to heed Tuesday's demand to stop the violence against peaceful demonstrators.
But it remains to be seen what steps Russia and China, who are traditionally reluctant to impose sanctions, will support.
US Secretary of State Hillary Clinton is due to travel to Geneva on Monday for a meeting of the UN Human Rights Council focusing on Libya.
The Swiss government has ordered an immediate freeze on assets belonging to Col Gaddafi and his associates.
On Thursday, Col Gaddafi told Libyan state television that Osama Bin Laden and his followers were responsible for the violence that was sweeping the country.
"Bin Laden... this is the enemy who is manipulating people. Do not be swayed by Bin Laden," he said in a telephone interview.
He said the young protesters were "trigger happy and they shoot especially when they are stoned with drugs".
"They put hallucinatory pills in their drinks, their milk, their coffee, their Nescafe."
Col Gaddafi also repeatedly referred to the western town of Zawiya, where fierce fighting has been reported, calling the situation there a "farce".
A witness said an army unit had attacked protesters there at a mosque with machine guns and rocket-propelled grenades, while a doctor said he had seen at least 10 dead as well as dozens of wounded.
State television announced that the air force had destroyed what was left of weapons depots in desert and rural areas outside government control.
There has also been a fierce battle for control of an airport near the opposition-controlled city of Misrata, about 200km (120 miles) from Tripoli. A doctor told the BBC that 13 bodies and 70 casualties had been brought to his hospital.
He said the people of Misrata could not afford to allow the government troops back in.
"If we said no more, no more fighting, who can stop this? Gaddafi will not stop this. If he occupies Misrata again he will kill everybody here."
Reports from the capital say that the bodies of people killed there have been cleared off the streets. Witnesses said pro-Gaddafi militiamen - including foreign mercenaries - were patrolling the Tripoli's main streets, firing in the air.
Security had also been stepped up outside key government buildings, and homes and hospitals had been raided in search of opposition supporters, they added.
"Now is the time of secret terror and secret arrests," one resident told the Associated Press. "They are going to go home-to-home and liquidate opponents that way."
The government has lost control of most of the country's east. Opposition leaders met on Thursday in the city of al-Bayda to demonstrate a united front against Col Gaddafi's grip on power.
In another blow to the Libyan leader, his cousin and close aide Ahmed Qadhaf al-Dam announced he had defected to Egypt in protest at the "grave violations to human rights".
The total number of deaths has been impossible to determine. Human Rights Watch says it has confirmed nearly 300 deaths, but the International Federation for Human Rights says at least 700 people have been killed.
A French doctor in Benghazi, Gerrard Buffet, told the BBC that as many as 2,000 people might have died in the east alone.
Ships and military aircraft have been sent to evacuate thousands of foreign nationals trying to flee the turmoil in Libya.
Turkey repatriated more than 7,000 of its citizens by ship; and ferries brought more than four thousand Chinese workers to Crete.
Larger numbers crossed overland into Egypt and Tunisia.
A US-chartered ferry carrying nearly 300 people remains stuck in harbour in Tripoli because of bad weather.
Meanwhile, a Venezuelan politician has told the UK's Daily Telegraph that one of Col Gaddafi's eight sons is hiding on the Caribbean island of Margarita.