To start with, Germany and Italy are reluctant to assert themselves in a region that still harbors memories of World War II occupation. France has been out front in the early days of the attack on Muammar Qaddafi's military. Britain, too, has played a part. Would London and Paris continue the campaign together? Given old rivalries, would one let the other take the lead?
Then there's the Arab League. After initially supporting the no-fly zone, Arab leaders are expressing misgivings about civilian casualties. They also appear to be worried that attacking an Arab strongman could come back to haunt them, since many are strongmen themselves. Egypt has a powerful enough military to make a difference in next-door Libya. But at a time of political change, Egypt's interim leaders would not want to be accused of aggression against a neighbor.
The Libyan rebels are weak. Qaddafi's forces are still strong enough to hold territory. Bottom line: While the US may not want to lead, it is difficult to see how the conflict ends without decisive action and a strong US role.