Rebel leaders and Nato have dismissed a call by Libyan leaderfor a ceasefire and negotiations.
The Benghazi-based rebel Transitional National Council said Col Gaddafi's offer was not credible and that the time for compromise had passed.
Nato officials said the alliance would not consider talks until government forces stopped attacks on civilians.
In a televised speech, Col Gaddafi said he was ready to talk to the US, UK and France if they stopped air strikes.
Officials had earlier warned rebels in the besieged city of Misrata that they had four days to lay down their arms or face an all-out assault.
At least two loud explosions were heard in the capital, Tripoli, on Saturday evening. One shook the hotel where foreign journalists are staying, not far from Col Gaddafi's sprawling Bab al-Aziziya compound.