By Ayman Al-Warfalli

BENGHAZI, Libya (Reuters) - Libya's government has reached a deal with an armed brigade controlling the Ras Lanuf and Es Sider oil ports to end a blockade and restart exports from the major terminals shut down since December 2014, officials said.

Officials from the government's presidential council and the oil guards gave no details of the terms or any date for when exports from the two ports would restart. But technical damage and opposition from the state-run National Oil Corporation may complicate any swift restart.

Reopening the ports would be a major boost for the OPEC member which since the 2011 war to topple Muammar Gaddafi has fallen deeper into turmoil that disrupted its oil output. Rival governments and a complex network of armed groups are vying for power and control of the country's oil wealth.

Members of the U.N.-backed Presidential Council were in Ras Lanuf late on Thursday at a joint conference with Ibrahim al-Jathran, head of the Petroleum Facilities Guards brigade, which controls Ras Lanuf and Es Sider ports.

"I am pleased on behalf of the Presidential Council to announce, as I am hopeful and optimistic, the resumption of the exports of Libyan oil from the ports," Presidential Council deputy Mousa Alkouni told reporters. "This is the beginning of the restoration of our country."

Ali Hassi, a spokesman for Jathran's PFG brigade, said no date had been decided for reopening the ports because that would depend on the National Oil Corporation. But he said an agreement had been signed between the council and Jathran's forces.

Armed factions, labor disputes and security threats from Islamic State militants have helped cut oil output to less than a quarter of the 1.6 million barrels per day (bpd) before the 2011 NATO-backed uprising that ousted Gaddafi.

Jathran's brigades led blockades of the ports starting in 2013 saying he was trying to prevent corruption in oil sales, though others have disputed his motives. He has also called for more autonomy for his eastern region.

Opening Ras Lanuf and Es Sider would add a potential 600,000 barrels per day of capacity to Libya's crude exports, though experts estimate damage from fighting and the long stoppage must be repaired before exports are at full capacity again.

The NOC has said damage from recent attacks by Islamic State, which expanded in the country's chaos, meant the ports would struggle to get beyond 100,000 bpd in the near term.

Beyond technical problems, NOC chairman Mustafa Sanalla has objected to any deal with Jathran saying it was a mistake to reward the brigade commander by paying to end his blockade of the oil ports.

Sanalla said a deal including payments would encourage other groups to disrupt oil operations in the hope of a similar payout. The NOC has also threatened to withdraw its recognition of the Presidential Council.

(Additional reporting by Ahmed Elumami in Tripoli; writing by Patrick Markey; Editing by David Evans)