Output of liquefied natural gas (LNG) from Indonesia's Bontang plant is expected to fall next year due to lower natural gas supplies, a senior official at the operator of the plant, PT Badak NGL, said on Friday.

Planned output this year at Bontang is expected to be 297 cargoes of 125,000 cubic metres each of LNG.

Total's Indonesian unit will produce 2.38 billion cubic feet per day (cfd) of natural gas in 2010 from its Mahakam block operation, down from 2.55 billion cfd in 2009.

Total is the main supplier of natural gas to Bontang to be processed into LNG.

We have just forecast that the LNG output will fall next year because of ageing gas fields causing lower gas supply, Agus Haryanto, president director of PT Badak NGL told Reuters.

The official did not give an estimated for drop.

I think demand for LNG will be a little bit higher next year, because economies will rebound, he said.

An official at Indonesian energy watchdog, BPMIGAS, estimated output from Bontang could fall between 6 to 7 percent in 2010 due to lower gas supply.

This is just an estimate, BPMIGAS and Total are still in talks about production plan next year, said the official, who declined to be identified.

A contract for the Mahakam block, in which France's Total and Japan's Inpex each hold 50 percent, will expire in 2017. Total has said previously it wanted to extend the contract of the block, offshore East Kalimantan on Borneo island.

Indonesia's state oil and gas firm Pertamina said last month that Total had agreed to give it 15 percent of the Mahakam block. Pertamina has previously indicated it wants to expand its upstream activities to boost oil and gas production, and that it was looking at several potential oil and gas fields.

(Reporting by Muklis Ali; Editing by Ed Davies)