he could be planning for a last stand . another saying it could put civilians in the cross hairs. both officials say they don t know what form a final offensive might take. recent nato air strikes are clearly upping the ante. our people there telling us they are under way again tonight, loud explosions being heard in tripoli within the past hour. opposition forces telling us they re making use of the air attacks to try to make progress on the ground. those forces now in the middle of a major push on zawhi, the keyport city on tripoli s doorstep. fierce artillery fire could be heard today. opposition fighters telling our sara sidener they could become moving on the capital within a matter of days. that could just be optimistic talk on their part. meantime the opposition says a form libyan prime minister has defected, fleeing tripoli with his family. no sign, though, that his former boss, muammar gadhafi, is going anywhere. and that s the potential problem. a potentially very