TRIPOLI- Libya's warring parties will soon start working to produce a single, consolidated state budget as part of efforts to find an agreement between them, the deputy head of the Tripoli-based government has told Reuters in an interview.

"Today we are looking to unify the budget so that the spending channel becomes one channel" between the two sides, said Ahmed Maiteeg, deputy prime minister in the internationally recognised Government of National Accord (GNA).

In September, Maiteeg struck an agreement with the GNA's rival, Khalifa Haftar, head of the eastern-based Libyan National Army (LNA), to end its eight-month blockade of oil output and exports with a deal to review how revenue was shared.

The OPEC member's oil production reached 500,000 barrels per day (bpd) this week and will rise to 550,000-560,000 bpd by the end of October and 1 million bpd by the end of the year, Maiteeg said.

All Libyan energy is produced by Libya's National Oil Corporation (NOC) with revenue funnelled through the Tripoli-based central bank. The GNA pays for the work of state institutions and salaries of many public employees across front lines.

However, the rival eastern-based administration in Benghazi has largely financed the LNA's war effort, accumulating billions of dollars in debt. Both sides have agreed to an external audit process for their finances, which started this year.

The GNA has prepared a budget for 2021 that is expected to be 45 billion-48 billion dinars ($38 billion-40 billion) including the funds for health, education and other public services across the country, Maiteeg said.

He added that he expected eastern side to present a forecast budget of 5 billion-8 billion dinars.

"Then the delicate technical work will begin, which is to unify these two budgets until one budget comes out," he said.

"It is the backbone of the agreement (with the eastern side) - the consolidation of the budget, not percentages of oil revenues," he said.

(Reporting by Reuters Libya newsroom Writing by Angus McDowall in Tunis Editing by Peter Graff) ((angus.mcdowall@thomsonreuters.com; Reuters Messaging: angus.mcdowall.thomsonreuters.com@reuters.net))