The US and the EU have again called on the Libyan leader Col Muammar Gaddafi to step down.
President Barack Obama said the US would take a wide range of actions to ensure Col Gaddafi surrendered power.
EU leaders meeting in Brussels agreed to "examine all necessary options" to protect the civilian population in Libya.
But they made no mention of imposing a no-fly zone over Libya in their final communique.
British and French leaders had wanted leaders of the European Union's 27 member states to draw up plans to prepare to help the Libyan rebellion, including the possibility of a no-fly zone.
This would prevent pro-Gaddafi troops launching attacks from the air - currently the primary advantage the regime's troops have as they push back the rebel forces.
The rebels had captured many eastern towns in recent weeks in an uprising that followed protests inspired by the revolutions in Egypt and Tunisia.
But many other EU leaders were not keen on the idea of a no-fly zone.