PARIS (Reuters) - France warned on Monday that an offensive by forces loyal to eastern Libyan commander Khalifa Haftar on oil sites risked sending the country backwards and urged the national unity government to be more inclusive to break a political deadlock.

The advance is the latest stage in a struggle for control of the OPEC nation's energy assets, extending chaos since the 2011 fall of Muammar Gaddafi that has splintered the North African country into rival armed fiefs.

Haftar has resisted the Tripoli-based unity government's efforts to integrate his self-styled Libyan National Army (LNA) into national armed forces. His seizure of oil ports could provoke a response from powerful western-based brigades allied with the government and deepen regional divisions.

"The situation in Libya is worrying and has gotten worse," French Foreign Minister Jean-Marc Ayrault told reporters in New York. "Haftar's offensive does not go in the right direction. There is a real risk of going backwards."

Ayrault said seeking to seize oil facilities for political purposes would lead Libya nowhere and it was crucial that the country's official National Oil Corporation (NOC) controlled fields under the auspices of the U.N.-backed Government of National Accord (GNA) of Prime Minister Fayez Seraj.

Libya is highly dependent on oil export revenue and needs to revive production to prevent economic collapse. The NOC called on Monday for the lifting of a blockade of western pipelines by a petroleum guard faction that it said had cost the country $27 billion in lost output since 2014.

"The production and commercialization of oil must be done in the framework of the NOC under government control, otherwise the risks of clashes in Libya are considerable," Ayrault said.

He said Seraj's government, which has struggled to apply its authority over much of the vast country, had to do more to set up a wider representative government that would also include Haftar in some capacity. "If Libya goes backwards then it risks reinforcing terrorism and Islamic State (militants)," he said.

(Reporting by John Irish; Editing by Bernadette Baum and Mark Heinrich)