Libya's new interim leaders have assured world leaders they will build a society full of tolerance and respect for the rule of law. Speaking at a Paris meeting, National Transitional Council (NTC) head Mustafa Abdel Jalil promised a new constitution and elections within 18 months. French President Nicolas Sarkozy, who chaired the meeting, stressed the need for "reconciliation and forgiveness". He said air strikes would go on as long as ex-leader Col Gaddafi was a threat. Mr Sarkozy said all 63 nations at the meeting were committed to returning frozen assets to the Libyan people. Col Gaddafi has still not been captured by the interim authorities. In an audio message broadcast on a loyalist TV channel on Thursday, he vowed he would never surrender. He was speaking on the 42nd anniversary of his emergence as Libya's leader, which until last year was an occasion for annual celebrations in the country. This year there were flag-waving celebrations in Tripoli's main square to mark the date - only the flags were the black, green and red colours of the NTC rather than the all-green of the Gaddafi regime, and the square is now known as Martyrs' Square, rather than the Green Square. Continued involvement Mr Sarkozy held the conference jointly with UK Prime Minister David Cameron - the two leaders who were instrumental in passing the UN resolution that allowed Nato forces to intervene in Libya. And both men stressed that Nato would continue its involvement as long as it was needed to protect civilians. "We are determined to continued with Nato strikes for as long as Mr Gaddafi and his supporters represent a threat to Libya," said Mr Sarkozy. And Mr Sarkozy said everyone had agreed to unfreeze assets blocked when Col Gaddafi was still in power. "After going around the table, it's about $15bn of Libyan assets in our countries that are immediately unfrozen," he said. He added that the NTC must engage in reconciliation in order to avoid the mistakes made in other countries. Mr Cameron urged the council to make sure perpetrators of the "unspeakable crimes" that were coming to light in Tripoli were brought to justice. Speaking to the BBC after the conference, Mr Cameron said that although there might be difficult days ahead for Libya, there had been a moral imperative for foreign intervention to "stop a slaughter". "Success in Libya means the Arab Spring can continue, and I think that's good for democracy," Mr Cameron told the BBC's Today programme. "Gaddafi was a monster, he was responsible for appalling crimes including crimes in this country, and the world is better off without him." Symbolism Meanwhile, Mr Jalil said it was now up to the Libyan people to push ahead with reconciliation. "It's up to you [the Libyan people] to accomplish what we promised: stability, peace and reconciliation," he said. "We have to make sure that we fulfil our side of the deal. We must have security in Libya. Tolerance and forgiveness must be promoted. The state of law must be respected." The BBC's Chris Morris in Paris says the gathering is full of symbolism, coming on the 42nd anniversary of Col Gaddafi's emergence as the leader of the coup that overthrew King Idris. But it is a sign that the NTC has been accepted by most of the world as the new face of Libya and that the international focus is beginning to move from conflict to reconstruction. The EU announced on Thursday that it had lifted sanctions on 28 entities - including oil firms and port authorities - to help the NTC get the economy moving again. The decision will take effect on Friday. The NTC received a further diplomatic boost on Thursday when Russia formally recognised its authority.