Libya's revolt erupted in February as part of anti-government protests spreading across the Middle East. Islamist groups stand to gain ground in neighboring Tunisia and Egypt, which shook off their dictators several months ago. Tunisia has taken the biggest steps so far on the path to democracy, voting Sunday for a new assembly, while Egypt's parliamentary election is set for next month.

Libya's struggle has been the bloodiest so far in the region. Mass protests quickly turned into a civil war that killed thousands and paralyzed the country. Gadhafi loyalists held out for two more months after the fall of the capital of Tripoli in late August. Gadhafi's hometown of Sirte fell last week, but Gadhafi's son and one-time heir apparent, Seif al-Islam, apparently escaped with some of his supporters.

The anti-Gadhafi forces enjoyed strong Western political and military support during their revolt, especially from the U.S., Britain and France, and NATO airstrikes were key to their victory.

Abdul-Jalil paid tribute to the Gulf Cooperation Council, a six-nation alliance led by Saudi Arabia, the Arab League and the European Union. NATO performed its task with "efficiency and professionalism," he said.

President Barack Obama congratulated Libyans on the declaration.

"After four decades of brutal dictatorship and eight months of deadly conflict, the Libyan people can now celebrate their freedom and the beginning of a new era of promise," he said