Nevertheless, Mr Obama has reluctantly concluded that he cannot afford to let Nato be humiliated in Libya, and that if America does not take a more active role in trying to shape the country's future, the danger is that it will slide into the abyss. Other considerations add to a sense of urgency among the Western policy-makers on Libya. The conflict has already prompted a quarter of a million people to flee across the border, mainly to Tunisia. The nightmare scenario for countries on the other side of the Mediterranean is that the northward flow of asylum-seekers from the region, which has increased recently, will turn into a flood if the conflict drags on interminably and life in Libya becomes intolerable.
The hope must be that US drones speed up the process of degrading Gaddafi's military capacity, relieve Misrata and force the authorities in Tripoli to get serious about negotiating an end to the conflict – one of the ingredients of a settlement being Gaddafi's departure. The concern in Washington will be that the US is being sucked into a war in which no end is in sight and in which it has no real stake – and that each new "modest contribution" only fuels calls for it to do more.