The Asian Development Bank said Wednesday it has approved a loan and political risk guarantee of up to $400 million for a project to build Uzbekistan's largest-ever petrochemical plant.

The ADB said the Surgil Natural Gas Chemicals Project would produce gas for commercial use and for conversion into chemical intermediates used in the plastics and textiles industries.

The project in the Karakalpakstan region will have annual supply capacity of about 4.5 billion cubic metres (157.5 billion cubic feet) of natural gas, it said in a statement, adding it is expected to be operational in early 2016.

Developer and operator Uz-Kor Gas Chemical is a joint venture between state-controlled National Holding Company Uzbekneftegaz and a consortium of South Korean firms -- Honam Petrochemical Corporation, the Korea Gas Corporation and STX Energy.

The Manila-based ADB said it would provide a 13-year loan of up to $125 million and a 13-year guarantee of up to $275 million.

It said the project's total cost was about $4 billion, with further financing to come from the Export Import Bank of Korea, Korea Trade Insurance Corporation, China Development Bank, National Bank of Uzbekistan, European export credit agencies and international commercial lenders.