World leaders have agreed to free up billions more in frozen assets to help Libya's interim rulers restore vital services and start rebuilding after a six-month war that ended a 42-year dictatorship.

In their first address on Thursday to the world since rebel forces overran Tripoli last week and drove out Muammar Gaddafi, Libya's interim leaders thanked Western powers for backing their revolt and urged Libyans to ensure a peaceful transition.

France, Britain and other powers, sitting down for talks with the National Transitional Council (NTC) 42 years to the day after Gaddafi seized power in a coup, vowed to keep up their military backing as long as needed but said the focus was now on reconstruction.

'We have committed to unblock funds from the Libya of the past to finance the development of the Libya of the future,' French President Nicolas Sarkozy told a news conference.

He said a total of $15 billion would now be freed up from Libyan assets frozen under sanctions. The figure included $3 billion the U.N. Sanctions Committee has approved for release in the United States and Britain and 1.5 billion euros ($2.16 billion) in France.

It also includes 2.6 billion euros of assets in Italy, a billion in Germany and 700 million euros in the Netherlands.

Interim Libyan council Chairman Mustafa Abdel Jalil told delegations from about 60 countries and international bodies that Libya would not let them down.

'The world bet on the Libyans and the Libyans showed their courage and made their dream real,' he said.

U.S. Secretary of State Hillary Clinton said U.N. sanctions should be lifted in a responsible way and the National Transitional Council (NTC) should get Libya's U.N. seat.

British Prime Minister David Cameron said the international community -- which will hold another meeting on Libya in New York later in September -- trusted the NTC and would stand by it. 'We cannot afford a failed pariah state on Europe's doorstep,' he said.

With the West anxious to avoid mistakes made in Iraq, the tight three-hour agenda of the 'Friends of Libya' talks focused on political and economic reconstruction, with the heads of Nato, the UN and the European Union also present.

Yet talks on the sidelines exposed early jostling for lucrative opportunities in restoring and expanding Libya's oil sector along with utilities and infrastructure.

'This is a potentially rich country. They have oil. They have resources frozen around the world. If we could find a way to move over to a democratic better-governed Libya, this could actually be a prosperous country,' Swedish Prime Minister Fredrik Reinfeldt told reporters.

Ahead of the talks, French Foreign Minister Alain Juppe said the priority was to help with humanitarian needs and restoring utilities and fuel, but investment opportunities loomed for a second stage.

'You know this operation in Libya costs a lot. It's also an investment in the future because a democratic Libya is a country that will develop, offering stability, security and development in the region,' he told RTL radio.

Abdel Jalil and interim Prime Minister Mahmoud Jibril laid out plans for a new constitution and elections within 18 months.

NTC spokesman Mahmoud Shammam said after the meeting that the members of the interim council did not intend to run for political office for four years.

Russia and China, which opposed the Nato intervention but will also be interested in bidding for contracts in a stable Libya, both sent delegations to the Paris talks.

British Foreign Secretary William Hague said he wanted to see a closer trading and economic relationship between Europe and Libya. He also said British companies would not be 'left behind' French and Italian rivals in jockeying for new business.

As well as big prospects for developing oil drilling, the end of the conflict will open up big opportunities for infrastructure, construction, electric power, telecoms, water and tourism companies who are keen to challenge the privileged position enjoyed by Italian firms under Gaddafi's long rule.

The NTC has said those who backed them will be rewarded. French companies have already gone in to assess the situation, but Britain plans no missions until the conflict is over.

French oil major Total , which was producing 55,000 barrels of crude per day in Libya before the conflict, said it has not yet discussed new investment possibilities.

'We have only talked about how we can help them restart production as quickly as possible,' Total Chief Executive Christophe de Margerie told reporters.

Diplomatic and oil industry sources denied a French newspaper report saying the NTC had agreed in April to give France priority access to 35 percent of Libyan oil in return for its backing.

De Margerie said he had no knowledge of a deal with France, as reported by the daily Liberation. Diplomatic sources said the report was false and Juppe said he was unaware of any deal.-Reuters