The South African President said in Tripoli that Libya had promised to "ensure that the two suspects would be available for the Secretary- General of the United Nations to take custody of them on or before 6 April 1999 for their appearance before the court".
Mr Mandela, accompanied by Colonel Gaddafi, read from a copy of letter from the Libyan leader which is to be sent to the Secretary-General, Kofi Annan.
Foreign Secretary Robin Cook, who jump-started the stalled negotiations seven months ago, said: "I welcome President Mandela's statement and am very much encouraged by what he has said."
The suspects, Abdel Basset Ali al-Megrahi and Lamen Khalifa Fhimah, are accused of planting the bomb which killed 270 people. If convicted, the letter says, they would serve prison sentences in Scotland under United Nations supervision and with access to a Libyan consulate to be established in Scotland.
The letter also insisted that sanctions on Libya, imposed in 1992 to extract the hand-over, will be lifted within 90 days of Mr Annan reporting that Libya has met UN requirements.Reuse content