Japan Post Holdings Co. will acquire a 7 percent stake in U.S. insurer Aflac Inc. in 2019, after gaining regulatory approval, and make it an affiliate four years after the purchase to expand their cooperation, both firms said Wednesday.

Following the stake purchase — worth about ¥270 billion ($2.4 billion) — Japan Post and Aflac will jointly develop new insurance products and make investments.

The Japanese financial and postal service firm will not get involved in the U.S. firm's management, they said.

The former state enterprise has been in partnership with Aflac Life Insurance Japan Ltd., selling Aflac's cancer insurance products at its post offices in Japan.

The share purchase is subject to regulatory approval in Japan and the United States, expected by the end of 2019.

Aflac's shareholder rules state that an entity holding ordinary shares of the company for four years will receive 10 units of voting rights per share. Japan Post's stake will eventually increase to 20 percent.

Under its three-year business plan through fiscal 2020, Japan Post is expanding its businesses in Japan and abroad by investing several hundreds of billions of yen in corporate acquisitions.