Despite thousands dead and the entire eastern half of the country out of his control, Muammar Gaddafi continues to hang on to Tripoli and his traditional tribal strongholds.

The question now is does either side have enough power to vanquish the other? The BBC:

BBC diplomatic correspondent Jonathan Marcus says the fighting underscores the fact that neither side seems to have the knock-out punch capable of defeating the other.

Col Gaddafi appears unable to re-capture the eastern part of his country, and for now his opponents seem unable to mount a major offensive against Tripoli.

A stalemate on the ground in Libya could be a serious problem for international diplomacy, our correspondent says.

Rebels were reported as saying pro-Gaddafi forces had been pushed back to Ras Lanuf, another oil terminal to the west of Brega, but were preparing another attack.

They are calling for UN-backed air strikes against pro-Gaddafi forces, but Western officials are cautious of military involvement.

Our correspondent says that diplomatic measures against Col Gaddafi were intended to hasten his departure and express support for the Libyan people's aspiration for freedom.

But there is now a danger that, having been painted into a corner, the Libyan leader may have little option but to cling on to power for as long as possible, he adds.

In other words, they are probably going to have to carry Gaddafi out on a litter before the violence will stop.