For now, it appears that the rebel charge westward has been reversed by Gaddafi troops, who have retaken the town of Nawfaliyah:

It took five days of allied air strikes to pulverize Libyan government tanks around the town of Ajdabiyah before Gaddafi’s troops fled and the rebels rushed in and began their 300-km (200-mile), two-day dash across the desert to within 80 km (50 miles) of the Gaddafi loyalist stronghold of Sirte.
But the rebel pick-up truck cavalcade was first ambushed, then outflanked by Gaddafi’s troops. The advance stopped and government forces retook the small town of Nawfaliyah, 120 km (75 miles) east of Sirte.
“The Gaddafi guys hit us with Grads (rockets) and they came round our flanks,” Ashraf Mohammed, a 28-year-old rebel wearing a bandolier of bullets, told a Reuters reporter at the front.

Read the full story here.