* Khalifa Hefta backed Gaddafi's 1969 coup
* Commanded anti-Gaddafi "exile army" for many years
* Hefta helped lead Libyan troops in Libya-Chad war
LONDON, April 1 (Reuters) - The military chief of Libya's rebels is a veteran Arab nationalist guerrilla foe of Muammar Gaddafi with past backing from the U.S. Central Intelligence Agency (CIA), according to a U.S. think-tank.
Khalifa Hefta is a former military commander who supported the 1969 coup that brought Gaddafi to power and became a member of Gaddafi's policy-making Revolutionary Command Council before breaking with him in 1987, the Jamestown Foundation said.
He has lived for the past 20 years in America, said a foundation research paper written by Derek Henry Flood, editor of Jamestown's Militant Leadership Monitor publication. It transliterates Hefta's name as Haftar.
"Today, as Colonel Haftar finally returns to the battlefields of North Africa with the objective of toppling Gaddafi, his former co-conspirator from Libya's 1969 coup, he may stand as the best liaison for the United States and allied NATO forces in dealing with Libya's unruly rebels," it said.
"The challenge before Colonel Haftar is whether he can graft his experience and know-how from wars and ideologies past onto a young movement already in disarray."
A rebel spokesman, Colonel Ahmed Bani, told Reuters in Benghazi on March 24 that Hefta would head the rebel army.
Reuters has repeatedly asked for an interview with Hefta but he could not immediately be contacted. An official of the rebel provisional National Council, Abdel Hameed Ghoga, said separately the military was being reorganised and the situation would become clearer in two days' time. He did not elaborate.
The CIA declined to comment.
The rebel army, made up largely of young, untrained volunteers, has been fighting to topple Gaddafi since shortly after a popular uprising against him broke out in mid-February.
Western allied planes have since pounded targets across Libya to enforce a no-fly zone. Foreign governments are debating what kind of further support, if any, they should offer.
The Jamestown paper described Hefta as "an old school secular Nasserist", referring to the pan-Arab ideology based on the ideas of the late Egyptian President Gamal Abdel Nasser.
Jamestown said that for many years Hefta had been the commander-in-exile of the Libyan National Army (LNA), the armed wing of the National Front for the Salvation of Libya (NFSL), a an exiled opposition group.
He had lived in the United States for twenty years, Jamestown said. It suggested that for some of that period he was pursuing LNA activities from the United States.