Spokesman Scott McClellan said an aeroplane carrying 25 tonnes of weapons programme components landed late on Monday in the US state of Tennessee.

McClellan heralded the move as "real progress" towards Tripoli's disarmament.

"While these shipments are only the beginning of the elimination of Libya's weapons, these shipments, as well as the close cooperation on the ground in Libya, reflect real progress," he told reporters on Tuesday. 

Economic sanctions

But he said it was too early to discuss the lifting of US sanctions on Libya because "there is more to do". 

Libyan leader Muammar al-Qadhafi agreed in December 2003 to end Tripoli's quest for unconventional arms.

He came to the decision after nine months of secret talks with Britain and the United States.

The surprise decision was taken to allow the country to focus on development and to normalise its relations with the US and Britain, Libyan officials said.

Washington bans most economic activity with Libya and bars its citizens from travelling to the country without government permission.