Azeri state energy company SOCAR is seeking new partners to help kick-start construction of its planned $16.5 billion oil, gas and petrochemicals plant and is already in talks with at least one possible investor, a senior executive said on Wednesday.

SOCAR said last year it had delayed completion of the complex at Sangachal, 60 kilometres (37 miles) south of the capital Baku, by four years to 2030 due to a lack of funds.

It said in March it would ask the central bank for a 1 billion manats ($952 million) loan for the project, but has not said if it received any support.

SOCAR Vice President Tofig Gakhramanov told Reuters the company had asked its financial consultant at the end of 2014 to find a company interested in helping back the project and had several proposals.

"One is a big Japanese company that has interested us most of all and we are now working with them," he said, without elaborating.

The first stage of the project, intended to replace SOCAR's ageing oil refinery as well as the Garadagh gas processing plant and facilities of chemicals firm Azerikimya, is estimated to be worth $2.1 billion. Building is expected to begin at the end of 2015 and to be completed by 2020.

SOCAR plans to attract 70 percent of the funds from investment firms and private companies, and the rest will be financed by participants of the project.

Once completed, SOCAR's annual oil refinery capacity will rise to 8 million tonnes of crude from 6 million tonnes.