State agency BP Migas which oversees upstream oil and gas regulations said that if the export contract is not fulfilled, Bontang would have to pay US$2 billion to the Japanese buyers.
The terminal now supplies 12 million tonnes of LNG to Japan, South Korea and Taiwan.
In an initial agreement still pending regulatory approval, Bontang has been contracted to export 25 million tonnes of LNG to Japan over a period of 10 years.
Separately, the large Natuna D-Alpha gas project is facing start-up delay due to uncertainty over production terms and conditions with operator ExxonMobil. The government said it awarded the operatorship to state energy firm Pertamina from 2006, which is being disputed by the US major. At best, the project could start up by the end of this decade if the dispute is sorted out.
Natuna D-Alpha, located 200km east of the West Natuna fields, is thought to hold 222 trillion cubic feet (tcf) of natural gas reserves, with about 46 tcf said to be commercially recoverable.