China Investment Corporation (CIC) will increase its stake in Engie E&P to 49 percent, after buying the initial 30 percent in 2011 for 2.3 billion euros (1.92 billion pounds), two sources close to the matter told Reuters.

Neptune Oil & Gas, set up in 2015 by private equity funds Carlyle Group (>> The Carlyle Group LP) and CVC Capital Partner to build a North Sea E&P company led by former Centrica CEO Sam Laidlaw, is set to announce the acquisition of a majority stake in Engie's business within weeks, banking and industry sources said.

Some details of the deal are yet to be finalised and the upcoming French elections could further delay the completion of the deal, according to the sources. The French state owns around 29 percent of the company, according to Engie's website.

The full value of the business is estimated at around $4 billion.

A Carlyle spokeswoman declined to comment. Engie and CIC were not immediately available to comment.

The size of CIC's stake following the sale became a major stumbling block as the Chinese partners initially sought to increase their holding to above 50 percent, the sources said.

The French utility, formerly known as GDF Suez, last year hired Bank of America-Merrill Lynch to exit from oil and gas exploration and stop burning coal. Its upstream assets span from the UK to Norway and Germany, Algeria, Egypt and Asia.

(Reporting by Clara Denina and Ron Bousso; Editing by Mark Potter)

By Clara Denina and Ron Bousso

Stocks treated in this article : Engie S.A., The Carlyle Group LP