Libyan leader Muammar Gaddafi has lashed back after an increase in Nato airstrikes with renewed shelling of the western city of Misrata, killing 10 rebel fighters.
The international alliance said it remained determined to keep pounding Gaddafi forces from the air, but would play no military role in the transition to democratic rule once his 42-year reign was over.
In Brussels, Nato Secretary-General Anders Fogh Rasmussen said Gaddafi's days in power were clearly numbered, making it imperative for the international community, the United Nations in particular, to gear up to help Libyans establish a new form of government.
"For Gaddafi, it is no longer a question of if he goes but when he goes," Fogh Rasmussen said at a meeting of the defence ministers from the 28 members of Nato.
"We do not see a lead role for Nato in Libya once this crisis is over," he said. "We see the United Nations playing a lead role in the post-Gaddafi, post-conflict scenario."
Nato said it was acting in accordance with the UN mandate to protect the Libyan people from Gaddafi, which did not include post-conflict peacekeeping.
French defence minister Gerard Longuet said: "Nato has a military vocation and rebuilding Libya is a civilian issue. So really simply, in order to rebuild Libya, if the Libyan people ask for it, because it is first of all an issue for the Libyan people, it is the job for civilian international institutions - and not military - to bring a response"
The Libyan rebels have also made it clear they do not want alliance ground forces in the country once the conflict is finished.
But they have welcomed the stepped-up Nato bombing campaign, which saw a record 66 strike sorties over Tripoli and the surrounding area on Tuesday.
"We've always felt that relentless, continuous strikes would hasten the departure of (Gaddafi) or at least the circle around him," said spokesman Jalal el-Gallal in Benghazi, the de facto rebel capital. "We're very glad that (Nato) is carrying out the actions, and it is a matter of time."