FORCES loyal to Libyan leader Colonel Muammar Gaddafi began air strikes against the rebel-held city of Benghazi today as the UK pushed for a no-fly zone.
According to witnesses on the ground, two planes bombed Benina airport in the city. The extent of the damage was not immediately clear.
The AFP news agency quotes a rebel spokesman as saying two of the planes attacking Benghazi were shot down.
Prime Minister David Cameron has been spearheading international calls for a no-fly zone and earlier this week Britain, France and Lebanon tabled a draft Security Council resolution authorising action.
The US administration had however been reluctant to give its backing to plan, amid fears that it could be dragged into messy conflict in another Muslim country at a time when they are still heavily committed in Afghanistan.
However, after eight hours of talks in the Security Council, Susan Rice, the United States ambassador to the UN, said that America was now prepared to support a new resolution and would be working "very hard" for a vote today.
"We are interested in a broad range of actions that will effectively protect civilians and increase the pressure on the Gaddafi regime to halt the killing and to allow the Libyan people to express themselves in their aspirations for the future freely and peacefully," she told reporters.
"The US view is that we need to be prepared to contemplate steps that include, but perhaps go beyond a no-fly zone, at this point, as the situation on the ground has evolved and as a no-fly zone has inherent limitations in terms of protection of civilians at immediate risk."
After days of stalling by the US over backing for a no-fly zone, diplomats said they were now talking of going even further - with airstrikes and the naval bombardment of Gaddafi's forces to help the rebels.
Despite the US about-turn, supporters of military intervention still need to overcome the objections of Russia and China which - as permanent members of the Security Council - can veto any resolution.
Two other important Security Council members - Germany and India - have also voiced strong reservations about becoming embroiled in Libya.
Foreign Secretary William Hague said that a strengthened draft resolution, tabled with the support of the Americans, called for "all necessary measures short of an occupation force" to protect the Libyan population.
"I must not pretend that agreement on this will be easy," he told MPs in a Commons debate on north Africa and the Middle East.
"We will do our utmost to ensure the passing of a resolution which places the maximum pressure on the Libyan regime and which extends protection to the beleaguered and oppressed civilian population."
Mr Hague acknowledged that a no-fly zone was not the "complete answer" to the current crisis.
"It may be one element that helps in this situation," he said.
On the ground Libyan rebels are battling to keep Gaddafi's forces from breaking into the key city of Ajdabiya.
Thirty people have been killed and at least 80 wounded in the fighting since Tuesday night, according to a senior hospital official in the city.
Gaddafi's army has surrounded Ajdabiya on three sides, leaving open only the road north to the larger rebel stronghold of Benghazi.
Charred vehicles, bullet-riddled pickup trucks and an overturned tank littered the desert road where pro-Gaddafi forces had fought up to the entrance of Ajdabiya, a city of 140,000.