TRIPOLI, Libya (AP) -- British Prime Minister David Cameron and French President Nicolas Sarkozy gave Libya's new rulers strong support during a landmark visit to Tripoli on Thursday, vowing to release billions of dollars more in frozen assets and to push ahead with NATO strikes against Moammar Gadhafi's last strongholds.

Cameron told the fugitive Libyan leader and his backers, "It is over. Give up."

The two were the first world leaders to travel to Tripoli since revolutionary forces, backed by NATO airstrikes, swept into the capital on Aug. 21 and forced Gadhafi into hiding. The visit aimed to give a significant boost to the National Transitional Council, the body of former rebels that is widely recognized as the new leadership but faces a major struggle in establishing its authority.

At a press conference alongside NTC chief Mustafa Abdul-Jalil and the NTC's prime minister Mahmoud Jibril, Cameron and Sarkozy both expressed their backing for the council. Cameron said he would push for the release to the NTC of billions of dollars in Libyan assets that had been frozen to punish Gadhafi's regime. To that end, he announced Britain and France would introduce a draft resolution to the U.N. Security Council on Friday authorizing the release of all Libyan assets.

"We have already unfrozen a billion pounds ($1.6 billion) worth of assets, but if we can pass the U.N. resolution that we will be putting forward with France tomorrow, there's a further 12 billion ($18 billion) of assets in the U.K. alone that we will be looking to unfreeze," he said.

Cameron also pledged the NATO mission would continue as Gadhafi loyalists are still battling revolutionary forces on three fronts in central and southern Libya. "There are still parts of Libya under Gadhafi's control, Gadhafi is still at large, and we must make sure this work is completed," he said.

He called on Gadhafi to surrender, saying "it is time for him to give himself up and time for Libyan people get the justice they deserve by seeing him face justice."

Britain and France led international support for the rebellion and their countries were major contributors to NATO airstrikes that helped turn the tide in favor of the opposition.

All that support could put France and Britain in a good position to cash in on lucrative trade and oil business once the country gets on its feet, but Sarkozy denied that was the goal.

"We ask for no preference with respect to Libyan assets or resources. What we did we did without a hidden agenda, but because we wanted to help Libya," Sarkozy said.

Sarkozy also said Gadhafi and others who "committed crimes" will be brought to justice but urged Libyans to avoid "vengeance" and seek unity and reconciliation.

The NTC and an executive committee it created are largely made up of technocrats - some of whom were once would-be reformers in Gadhafi's regime who grew disillusioned and left - and representatives from town and cities around the country. It not only faces the task of winning control over the last Gadhafi strongholds, it also must rein in the numerous armed groups and factions under the former rebel umbrella.

The flow of more of the frozen funds from abroad could boost its hand.

So far, the U.N. has approved the unblocking of about $6 billion from banks in the United States, Britain and France. A Cameron spokeswoman, who spoke on condition of anonymity in line with policy, said a new United Nations Security Council resolution authorizing the release of all frozen Libyan assets has support of all five permanent members. Analysts estimate that as much as $110 billion is frozen in banks worldwide.

Britain has also won approval from the U.N. sanctions committee on Libya to release a further $950 million immediately to fund public sector salaries, she said. Britain will also offer funds for weapons decommissioning, mine clearance, medical assistance for those with grave combat injuries and specialist help in locating and secure chemical weapons.

NATO forces continued to go after the holdout loyalist forces. Airstrikes hit targets 24 targets on Wednesday, including several radar systems and surface-to-air missile systems near the three main strongholds of Gadhafi's supporters - his hometown of Sirte, Bani Walid and Sabha - as well as smaller holdouts Waddan and Zillah, the alliance said.

Cameron and Sarkozy were greeted at Tripoli's airport by NTC leaders. Security was tight in the coastal capital, with Apache helicopters buzzing over the Mediterranean Sea.

Several Libyans clapped and reached out to touch the British and French leaders as they walked toward a hospital, where they met with amputees and other patients who were injured in the fight against Gadhafi. Doctors, nurses and other staff also offered a round of applause and chanted Libyan freedom slogans.

The two leaders then flew to the eastern city of Benghazi, which was the birthplace of the rebellion. A crowd gathered at the city's central square hoping to see them, with banners saying, "Thank you Sarkozy. Thank you France" and "Thanks UK."

One of the choppers flying overhead stood out. It was a different color and was carrying the Libyan flag. The audience on the ground cheered when they spotted it. "God is Great," they said and clapped.

Boats patrolled the sea and helicopters flew overhead, including one that carried the new Libyan tricolor flag. The crowd on the ground cheered when they spotted it and chanted "God is Great."

French Finance Minister Francois Baroin also said the visit was not about landing economic deals but about showing support for the former rebels who ousted Gadhafi. Asked in an interview on France-Info radio whether there were economic arguments for the visit, Baroin said, "we are not at that stage."

France's focus is not yet on reconstruction contracts but on supporting the interim leadership and pursuing "the last pro-Gadhafi pockets," he said.

French news reports said Sarkozy was accompanied by dozens of French riot police, an unusual move that underlined the continued worries over security.

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Associated Press writers Angela Charlton in Paris and Rami al-Shaheibi in Benghazi contributed to this report.

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