"Qaddafi's regime has lost all credibility," Abdel Hafiz Ghoga, spokesman for the rebel's transitional national council, said in a statement.
The Libyan leader had repeatedly offered ceasefires only to continue violating human rights, it said.
"The time for compromise has passed. The people of Libya cannot possibly envisage or accept a future Libya in which Qaddafi's regime plays any role," it said.
In a speech broadcast on Libyan state television, Qaddafi offered to order a ceasefire and start negotiations provided that NATO stop its strikes against his forces but he refused to give up power, as rebels and Western powers demand.
"(Libya) is ready until now to enter a ceasefire," Qaddafi said. "We were the first to welcome a ceasefire and we were the first to accept a ceasefire but the Crusader NATO attack has not stopped. The gate to peace is open."
The rebels' military spokesman, Colonel Ahmed Bani, also said Qaddafi was "playing dirty games".
"He doesn't speak honestly. We don't believe him and we don't trust him," Bani told Reuters.