Rebels in Ras Lanuf on Monday. (Via Twitter user @hamish6PM)

Libyan rebels under heavy fire retreated more than 100 miles on Tuesday.

Without help from NATO airstrikes, the "lightly armed" rebels struggled to advance in the face of mortar and artillery fire. They failed to capture Gaddafi's hometown of Surt. Instead, they were pushed backed to Bin Jawad and then Ras Lanuf. 

Gaddafi's forces charged ahead, a product of better organization, skills and weaponry. The rebels seem to need more than NATO forces in the sea and the air to definitively make progress in the battle. U.S. diplomat Susan Rice said Tuesday that the idea of arming the rebels had not been completely ruled out.

U.S. Secretary of State Hillary Clinton, meeting with other world leaders about how to continue the operation in Libya, said they would not stand down until Gaddafi stopped attacking his own people. Among the options discussed at the meeting in London was were to send Gaddafi should he be placed in exile.

A day after President Barack Obama explained the America commitment to care for civilians around the world, the Pentagon said the Libyan operation has cost the government more than half a billion dollars. The costs going forward should be about $40 million a month, mostly on weaponry.

Allied airstrikes on Tuesday evening did appear to bombard the capitol of Tripoli farther to the West while Gaddafi forces shelled nearby Misrata.

Reach deputy editor Paresh Dave here. Follow him on Twitter: @peard33.