U.S. energy giant ConocoPhillips has asked Indonesia's energy ministry to extend its operations in the Corridor natural gas block after its contract ends in December 2023, a ministry official said.

ConocoPhillips (Grissik) Ltd had submitted a letter regarding its Corridor plans but still needed to submit a formal proposal, Oil and Gas Director General Djoko Siswanto told reporters on Sept. 3.

Without a formal proposal this month, the right to operate the block would be "given to Pertamina", Siswanto said, noting that the sizeable output from the block in South Sumatra province would be attractive to the state oil company.

ConocoPhillips (Grissik) Vice President for Commercial and Business Development Taufik Ahmad confirmed that the company had sent the letter expressing its interest in extending its Corridor operations.

However, Ahmad said that Conoco "still needed more comprehensive discussions" with SKKMigas - Indonesia's upstream oil and gas regulator - before it could submit a proposal for the extension.

Pertamina spokesman Adiatma Sardjito told Reuters by text message that the state energy company had not submitted a proposal to take over as operator of the Corridor block but that the matter was "still being evaluated".

Indonesia is pushing to nationalize more of its oil and gas assets as it tries to reduce imports and boost government revenue, but experts warn that this approach discourages investors and global energy companies with expertise crucial to maintaining its energy output.

Corridor produced 828.4 million standard cubic feet of natural gas per day (MMcf/d) on average from January to July this year and is expected to churn out 810 MMcf/d in 2019, recent SKKMigas data showed.

Repsol holds a 36% participating interest in the block.

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