The CEO of Rakuten, the company that agreed to acquire Viber for $900 million in February, aims to use the messaging app to expand its user base to as much as two billion people.

In an interview with Bloomberg, Hiroshi Mikitani said the Japanese e-commerce company is planning to increase Viber’s additions of 600,000 users per day to one million.

If this can be achieved, around 365 million users would be added annually, meaning the 300 million users Viber already has could be doubled in less than 12 months.

Rakuten already has around 200 million users.

Mikitani is looking to expand Rakuten beyond its core online marketplace business, with investments in mobile apps and online video.

It is now competing with the likes of Amazon, Facebook and Softbank, the Japanese group with a stake in Chinese e-commerce giant Alibaba, and rumoured to have plans to acquire a stake in the mobile messaging provider LINE, as well as controlling operators in the US and Japan.

Mikitani said he plans to operate Viber it as a standalone business; add games to the messaging platform; and develop synergies with the rest of Rakuten’s business, which also includes finance.

The Rakuten loyalty programme will be used to give online shopper points to make purchases within Viber, which Mikitani hopes will further drive uptake.

Rakuten’s acquisition of Viber was announced just before Facebook’s $19 billion acquisition of WhatsApp. Facebook CEO Mark Zuckerberg said he expects WhatsApp to reach one billion users over the next few years.

The $900 million Rakuten spent on Viber means it is paying $3 per user, compared to the $42 per user Facebook is paying with WhatsApp.

According to Bloomberg, Rakuten’s shares slumped by as much as 14 per cent following the announcement of the Viber deal. This may be due in part to Viber’s $29.5 million net loss in 2013.