Starbucks is planning a big push behind its loyalty program, with plans to double membership by the end of the year.

Starting in May, the world's biggest coffee company says members will be able to earn points when they buy bags of Starbucks coffee at supermarkets. Customers would have to go online and enter a code on the bag to get their point.

Starbucks Corp. had announced the move last year but hadn't said when it would be available. The details on the rollout were to be announced at the company's annual meeting Wednesday.

The Seattle-based company says a number of other marketing campaigns will also help push its membership to 9 million by end of this fiscal year, up from its 4.5 million current members. Starting next month, for example, customers will also be able to earn points at the company's recently acquired Teavana shops.

A Starbucks spokeswoman did not have details on how spending patterns change when people join the loyalty program.

The My Starbucks Rewards program was launched in 2009 and gives people free drinks and food based on the number of points they earn. People earn one point for every purchase, regardless of how much they spend.

Starbucks shares rose 29 cents to $57.12 in midday trading Wednesday.