SoftBank Corp. is seeking to buy a stake in Line Corp., the mobile-messaging service controlled by South Korea's Naver Corp., sources said.

Line has received at least one other offer for all or some of the company, prompting it to slow preparations for an initial public offering, said two of the sources, asking not to be identified as the information is private. The Tokyo-based Line, which has about 340 million users, may be worth as much as $14.9 billion, according to BNP Paribas SA estimates.

Services that rely on Internet access to let users send messages or make calls for free are displacing traditional text-messaging services offered by phone companies. This month Facebook Inc. said it will pay as much as $19 billion to acquire WhatsApp Inc., just days after Rakuten Inc. agreed to pay $900 million for rival Viber.

SoftBank founder Masayoshi Son has held talks with Line about a purchase, one source said. Japan's No. 3 wireless company, which also controls Sprint Corp. in the U.S., has been acquiring stakes in providers of content, including China's Wandoujia and Finnish game maker Supercell Oy.

While Line is still aiming for an initial public offering later this year, it wants to take some time to evaluate the proposals, another source said. Selling a stake to a larger company could help Line increase its valuation ahead of the share sale, according to that source.

Mitsuhiro Kurano, a Tokyo-based spokesman for SoftBank, and Fumiko Hayashi, a Tokyo-based spokeswoman for Line, declined comment. Nam Ji-woong, a spokesman for Naver, said he could not immediately comment.

Line is the No. 1 mobile messenger service in Japan, Taiwan and Thailand — ahead of Facebook Messenger in all three countries, said a Feb. 20 report from Samsung Securities Co. citing data from researcher App Annie Ltd.