SEOUL (Reuters) - South Korea's Hankook Tire & Technology Co Ltd has signed a preliminary agreement to acquire a stake worth 1.7 trillion won ($1.25 billion) in Hanon Systems, it said on Friday, which would make it the majority shareholder.

Hankook Tire, a business unit of Hankook & Company Group, said in a regulatory filing that its board had approved a plan to acquire private equity firm Hahn & Company's 25% stake in Hanon Systems, an automotive thermal and energy management solution company. It will also buy 12.2% of the new shares to be issued through a capital increase.

Hankook Tire would then become the biggest shareholder of Hanon Systems with a 50.5% stake, it added.

Hankook Tire said in a statement that the company plans to complete the acquisition process by the end of the year.

($1 = 1,361.7100 won)

(Reporting by Heekyong Yang; Editing by Kirsten Donovan)