Libyan tanks and warplanes intensified their offensive against rebels on Tuesday, as the United States stressed that any no-fly zone to hobble Muammar Gaddafi's forces had to have global backing.
Rising casualties and threats of hunger and a refugee crisis have increased pressure on foreign governments to act, but many are fearful of moving from sanctions alone to military action.
"We want to see the international community support it (a no-fly zone)," Secretary of State Hillary Clinton said. "I think it's very important that this not be a US-led effort."
She told Sky News the United Nations should make the decision on Libya, not the United States.
"We've called for Colonel Gaddafi to leave," she added. "When a leader turns against his own people, that is the end."
US President Barack Obama and Prime Minister David Cameron agreed the "common objective" was an end to violence and the departure of Gaddafi, the White House said.
In a phone call the two leaders "agreed to press forward with planning, including at NATO, on the full spectrum of possible responses, including surveillance, humanitarian assistance, enforcement of the arms embargo, and a no-fly zone."
Britain and France are seeking a UN resolution to authorise such a zone to ground Gaddafi's aircraft and prevent him moving troops by air. Russia and China, who have veto power in the UN Security Council, are cool towards the idea, which would be likely to require bombing of Libyan air defences.
Hafiz Ghoga, spokesman for the rebel National Libyan Council, told a news conference in the rebel base of Benghazi:
"We will complete our victory when we are afforded a no-fly zone. If there was also action to stop him (Gaddafi) from recruiting mercenaries, his end would come within hours."
In besieged Zawiyah, the closest rebel-held city to Tripoli, trapped residents cowered from the onslaught on Tuesday.
"Fighting is still going on now. Gaddafi's forces are using tanks. There are also sporadic air strikes ... they could not reach the centre of the town which is still in the control of the revolutionaries," a resident called Ibrahim said by phone.
"Many buildings have been destroyed including mosques. About 40 to 50 tanks are taking part in the bombardment."
Libyan television showed two of its reporters meeting residents on Tuesday in what it said was "liberated Zawiya."
Rebels still controlled the central square of the town, 50 km (30 miles) west of Tripoli, on Tuesday and were using loud hailers to urge residents to defend their positions, said a Ghanaian worker who fled on Tuesday.
Sky television footage of fighting in Zawiyah over the weekend showed crowds fleeing gunfire and a blood-spattered hospital crammed with the wounded, some making victory signs from stretchers. It showed bodies of dead soldiers, others it said had switched sides, and captured tanks.
A government spokesman insisted troops were mostly in control on Tuesday. "Maybe 30-40 people, hiding in the streets and in the cemetery. They are desperate," he said in Tripoli.
A Libyan man who lives abroad said he spoke by phone on Tuesday to a friend in Zawiyah who described desperate scenes.
"Many buildings are completely destroyed, including hospitals, electricity lines and generators," he said.
"People cannot run away, it's cordoned off. They cannot flee. All those who can fight are fighting, including teenagers. Children and women are being hidden."
Foreign reporters have been prevented from entering Zawiyah and other cities near the capital without an official escort.
In the east, much of which is under rebel control, warplanes bombed rebel positions around the oil port of Ras Lanuf.
Revolutionary euphoria seemed to have dimmed. "People are dying out there. Gaddafi's forces have rockets and tanks," Abdel Salem Mohamed, 21, told Reuters near Ras Lanuf. "You see this? This is no good," he said of his light machinegun.
Air strikes hit rebels behind the no-man's land between Ras Lanuf and Bin Jawad, 550 km (340 miles) east of Tripoli. The towns are about 60 km (40 miles) apart on the strategic coast road along the Mediterranean.
One strike smashed a house in a residential area of Ras Lanuf, gouging a big hole in the ground floor.
Mustafa Askat, an oil worker, said a bomb had wrecked a water pipeline and this would affect water supplies.
"We have a hospital inside, we have sick people and they need water urgently," he said.
A convoy from the UN food agency was scheduled to reach the rebel-held port of Benghazi on Tuesday to deliver the first food aid in Libya since the revolt erupted three weeks ago.
The rebel army -- a rag-tag outfit largely made up of young volunteers and military defectors -- made swift gains in the first week of the uprising which saw them take control of the eBut their momentum appears to have stalled. Some government troops who had been besieging the rebel-held city of Misrata left on Tuesday, driving east towards Sirte with pro-Gaddafi forces coming from Tripoli, a resident said by phone.
Sirte, birthplace and stronghold of Gaddafi, lies on the road to the emerging front that divides the country along ancient regional lines, with oil facilities in the middle.
REBEL LEADERS LOBBY EU
Gaddafi calls rebels drug-addled youths and al Qaeda-backed terrorists, and said he will die in Libya rather than surrender.
He visited a Tripoli hotel where foreign journalists are staying late on Tuesday and gave short interviews to French and Turkish television crews.
Representatives of the Libyan opposition met EU foreign policy chief Catherine Ashton in Strasbourg and planned to speak at the European Parliament on Wednesday.
Mahmoud Jebril, head of the crisis committee of the National Libyan Council, said the EU should recognise the council as the sole legitimate representative of the Libyan people.
"Empowering the people to continue their armed struggle against Gaddafi can be done by different means," he said. "A no-fly zone is one of them, supplying the peoples with arms."
EU states agreed to add the $70 billion (43 billion pounds) Libyan Investment Authority to a sanctions list on Tuesday. The embargo already covers 26 Libyans including Gaddafi and his family.
A Libyan official said Finance Minister Abdulhafid Zlitni had temporarily taken over as head of the central bank because its governor Farhat Omar Bin Guidara was abroad. Bin Guidara said in Dubai he disputed the legality of the decision.
The Libyan uprising is the bloodiest of a tide of protests against autocratic rulers in North Africa and Middle East which has already seen the leaders of Tunisia and Egypt overthrown.
The phenomenon has left the West struggling to formulate a new direction for a region that sits on vast reserves of oil.
Brent crude futures for April delivery fell to about $113 a barrel on Tuesday, after rising sharply on Monday.
ast and challenge the government near Tripoli.