Japanese oil refiner Idemitsu Kosan is in talks to acquire a smaller rival, Showa Shell Sekiyu for $4.2 billion in a deal that could create the country's second largest player in the domestic gasoline market, a person with knowledge of the issue said.

Idemitsu and Showa Shell aim to reach an agreement early next year, the person said, asking not to be identified because the deal is not public yet.

Idemitsu aims to buy shares in Showa Shell in a tender offer which could be worth as much as 500 billion yen ($4.2 billion), the person said.

The united company would control 30 per cent of Japan's gasoline market, the second largest after JX Holdings.

Idemitsu said in a statement on Saturday that it is in talks on various possibilities with Showa Shell but at this point nothing has been decided.

Showa Shell said on the same day that Idemitsu is one of the companies that it is in talks for possible management options and also need nothing was settled.-Reuters