An interim study shows the reserves are a fourth of an initial estimate of 96 million metric tonnes, Chief Executive Choo Kang-soo told lawmakers. A final estimate will be ready in January, Choo said.

In 2008, the government said the state-run utility will lead a group of South Korean companies in a US$1.83 billion venture to develop a gas field and build a chemical plant in Uzbekistan.

The group and state oil company Uzbekneftegaz agreed to set up a 50-50 joint venture for the project, which will start production in 2012, the energy ministry said at that time.

Total investment cost may increase 39% to $3 billion from an initial projection, Choo said.