Line Corp., operator of Japan's most popular mobile-messaging service, is preparing for a dual listing in Tokyo and New York before Japan Post Holdings Co.'s initial public offering, people with knowledge of the matter said.

The Tokyo-based company aims to sell shares around September to avoid competing for investors with state-owned Japan Post, the people said, asking not to be named as the information is private.

The government has said it will raise as much as ¥2 trillion ($16.5 billion) from a Japan Post listing later in the year. Line has resumed work with Morgan Stanley and Nomura Holdings Inc. on plans for its offering, which could value it at more than ¥1 trillion, the people said.