The French defence minister has suggested a new UN Security Council resolution may be needed for Nato allies to achieve their goals in Libya.
Gerard Longuet was speaking after a joint letter by the US, UK and French leaders said there could be no peace while Col Muammar Gaddafi was in power.
The current UN resolution makes no mention of regime change.
Signs of division remain within Nato, which is struggling to find additional combat aircraft for its strikes.
Nato pilots are enforcing the current UN resolution to establish a no-fly zone and to protect civilians in Libya, which has effectively been split between forces for and against Col Gaddafi since a revolt against his rule began in mid-February.