Rebel forces were bearing down on Sirte, Muammar Gaddafi's home town and a key government stronghold, today, setting the stage for a bloody and possibly decisive battle.
The opposition made new headway in its rapid advance westward through oil towns and along stretches of empty desert highway towards Sirte and beyond to the big prize - the capital, Tripoli.
In Sirte, a brigade headed by one of the Libyan leader's sons was digging in to defend the city.
But the rebels remain woefully outgunned by Gaddafi's forces, who swept the insurgents from positions in eastern Libya until the international intervention forced government troops to withdraw.
Rebels acknowledged they could not have held their ground without international air and cruise missile strikes. Libya state television reported new Nato air strikes after nightfall, targeting "military and civilian targets" in the cities of Garyan and Mizda about 40 miles and 90 miles respectively from Tripoli.
Speaking in Washington early today, President Barack Obama declared the goal of the mission was not to depose Gaddafi, saying he would work to replace him by "non-military means".
He said the US and its allies moved fast to protect Libya's civilians from imminent massacres by Gaddafi's forces "and as president, I refused to wait for the images of slaughter and mass graves before taking action".
Nato insisted that it was seeking only to protect civilians and not to give air cover to an opposition march, but that line looked set to become even more blurred. The air strikes are now clearly enabling rebels bent on overthrowing Gaddafi to push towards the final line of defence on the road to the capital.
Vice Admiral William Gortney, staff director for the Joint Chiefs of Staff, said the US was hitting Libyan targets with Thunderbolts and AC-130 gunships, aircraft that can fly low enough to support ground operations.
There was growing criticism from Russia and other countries that the international air campaign was overstepping the bounds of the United Nations resolution that authorised it.
The complaints came at a critical transition in the campaign from a US to a Nato command. That threatens to hamper the operation, as some of the 28 Nato member nations plan to limit their participation to air patrols, rather than attacks on ground targets.
Yesterday rebel fighters moved about 70 miles west from the coastal oil terminal and town of Ras Lanouf to just beyond the small town of Bin Jawwad, where their push was halted by government fire along the exposed desert highway and the heavily-mined entrance to Sirte.
The rebels are currently just 60 miles from Sirte, the bastion of Gaddafi's power in the centre of the country.
If they take control of that, there is only the largely rebel-held city of Misrata - and then empty desert - in the way of the capital. Sirte could therefore see some of the fiercest fighting of the rebellion, which began on February 15.
"Gaddafi is not going to give up Sirte easily because straight away after Sirte is Misrata, and after that it's straight to Gaddafi's house," said Gamal Mughrabi, a 46-year-old rebel fighter. "So Sirte is the last line of defence."
He said there were both anti- and pro-Gaddafi forces inside Sirte.
Some residents were fleeing Sirte as soldiers from a brigade commanded by Gaddafi's son al-Saadi and allied militiamen streamed to positions on the city's outskirts to defend it, witnesses said. Sirte was hit by air strikes on Sunday night and yesterday morning, witnesses said, but they did not know what was targeted.
The city is dominated by members of the Libyan leader's Gadhadhfa tribe. But many in another large Sirte tribe - the Firjan - are believed to resent his rule and rebels are hoping to encourage them and other tribes there to help them.
"There's Gaddafi and then there's circles around him of supporters. Each circle is slowly peeling off and disappearing," said General Hamdi Hassi, a rebel commander speaking at the small town of Bin Jawwad, just 18 miles from the front. "If they rise up, it would make our job easier."
Sirte, which houses a significant air and military base, is crucial both for its strategic position and its symbolic value. Over the years, Gaddafi has made it effectively Libya's second capital, building up what had been a quiet agricultural community into a city of 150,000 with lavish conference halls where Arab and African summits were held.
The Gulf nation of Qatar recognised Libya's rebels yesterday as the legitimate representatives of the country - the first Arab state to do so. Qatar is also one of only two Arab states - the other is the United Arab Emirates - that is contributing fighter planes to the air mission.
But Gaddafi is not on the defensive everywhere. His forces continued to besiege Misrata, the main rebel holdout in the west and Libya's third-largest city. Residents reported fighting between rebels and loyalists who fired from tanks on residential areas.
In a late development, The official Tunisian news agency said Libyan foreign minister Moussa Koussa arrived in Tunis on what it called a "private visit". No further details were available.