NATO Secretary General Anders Fogh Rasmussen said Wednesday that Libyan leader Muammar Gaddafi's departure from power was only a matter of time and the international community must be prepared for the post-Gaddafi era.

"The question is not if Gaddafi will go, but when ... It could take some time yet. It could happen tomorrow," the NATO chief told a forum hosted by Carnegie Europe in Brussels.

International mediation efforts on Libya have made little progress while NATO escalated its air strikes against Gaddafi's forces.

Rasmussen said the alliance had decided to extend its mission in Libya for another 90 days and would keep up the military pressure "as long as necessary" to pave the way for a political solution.

The NATO chief said he did not see a major role for the 28-member alliance after it had completed its UN-mandated operation.

"But once Gaddafi has gone, the international community must help the Libyan people ensure a peaceful and orderly transition to democracy. And it must start to plan and prepare for that day," he said.

In addition, Ramussen said NATO was well suited to help Libya reform its military sector.

"We stand ready to share this collective experience and expertise, also for the benefit of Libya ... I could imagine providing assistance in building Libya's new Ministry of Defence, a joint General Staff and a National Security Agency," he said.