ExxonMobil Indonesia's Cepu block will likely not reach full production until August or September 2014, behind the initial schedule for May 2014, an official from the oil and gas regulator told Reuters on Monday.

"Initially we were expecting the project would deliver (full) production in May 2014, but I'm not sure if we can deliver it in May or not ... Probably going up to August or September," said Gde Pradnyana, operations controller at the regulator.

Cepu is producing 24,000 barrels per day and its target production of 165,000 is hoped will boost Indonesia's dwindling crude output.

Pradnyana said Cepu was a top priority for the government, and that its management and delays in production were one of the reasons why the regulator had decided not to extend its assignment for ExxonMobils local CEO, Richard Owen.

(Reporting by Fergus Jensen)