ANALYSIS - As Libya showdown looms, postwar worries build

LONDON (Reuters) - Tripoli might be cut off and Libya's war moving to its endgame, but even if Muammar Gaddafi avoids a bloody finish his departure could usher in a new period of instability and uncertainty.

Libya's rebels said on Tuesday they had completed moves to cut off roads to the capital after rapid advances in the west. The defection of a senior Gaddafi security official further reinforced the image of crumbling central authority.