Starbucks Corp. is buying the rest of its East China joint venture in a $1.3 billion transaction, marking the biggest deal ever for a company that sees China as a huge growth opportunity.

The Seattle-based coffee chain will acquire the remaining 50 percent of the business from partners President Chain Store Corp. and Uni-President Enterprises Corp. Starbucks also is divesting its 50 percent stake in a separate joint venture in Taiwan, according to a statement Thursday.

The move underscores Starbucks' bet that China will be one of the company's top sales drivers in coming years. It's wagering that the nation's growing middle class and urbanization will give it a huge population of potential coffee drinkers to tap.