After 14 years of defiance and denials, Libya took formal responsibility on Friday for the bombing of Pan Am Flight 103 over Lockerbie, Scotland, an attack that killed 270 people and cemented Libyan leader Moammar Gadhafi’s international isolation. Libya agreed to pay $10 million to each victim’s family and said in a letter delivered to UN Security Council that it is responsible for the actions of Libyan intelligence agent Abdel Basset Ali Megrahi, convicted of plotting to destroy the airliner with a bomb hidden inside a suitcase.‘‘Libya as a sovereign state accepts responsibilities for the actions of its officials,’’ Libyan ambassador Ahmed A. Own said in the letter. He pledged Libyan cooperation with the continuing investigation into the bombing.The Bush administration welcomed the statement, negotiated by US and UK diplomats, but described it as a minimal first step in satisfying US concerns about Libyan behaviour, notably recent arms development and what a senior official described as ‘‘meddling’’ in African civil wars. A US official said Libyan authorities will now be expected to reveal more details to criminal investigators about the December 21, 1988, attack. Friday’s developments, intended by Libya as a bid for redemption and renewed foreign trade, represent a dramatic step in the quest to hold Gadhafi and his government accountable for one of the deadliest acts of terrorism in US history.The statement of accountability stops short of implicating Gadhafi or anyone in his circle, despite the ruling by a Scottish court in 2001 that ‘‘the clear inference’’ of evidence in the case is that ‘‘the conception, planning and execution of the plot . was of Libyan origin.’’According to US officials, the statement should lead to a UN Security Council vote as early as next week lifting sanctions suspended in 1999. Libya will have to demonstrate ‘‘tangible changes in behaviour’’ if it wants relations with US to improve, said a senior US official after Powell and Assistant Secretary of State William Burns met with Pan Am 03 families at the State Department.The administration, he said, has ‘‘quite significant concerns’’ about Libyan efforts to develop WMDs and extend the range of its missiles. The CIA said in an unclassified report to Congress this year that Libya has a ‘‘continued interest in nuclear weapons’’ and ‘‘still appeared to be working hard’’ to develop biological and chemical arms. The Libyans requested the lifting of sanctions immediately, once the $2.7 billion has been deposited. Payments to the Pan Am 103 families are tied to Libya’s success in ending the international sanctions. (LAT-WP)