Tricky...

NATO's remit in Libya is the protection of civilians.  There are those (me included) who think they have gone well beyond that, but that's an argument for another time.  But what will happen if the rebels attack Sirte and civilians start dying there as a result?  What would be the difference between that scenario and what was about to happen to Benghazi, which was what brought NATO in in the first place?  Would NATO start targetting the rebels to protect the Sirte civilians?  There may be interesting times ahead.