Starbucks Corp.  (SBUX) - Get Report  fell about 4% by 1:30 p.m. Thursday after a triple-threat of reports on China's slowdown, a broad market selloff on bad news from Apple Inc. (AAPL) - Get Report , and the brewing story about Luckin Coffee -- a growing rival to Starbucks in China -- that reportedly expects to open 4,500 shops by the end of the year.

Luckin -- a year-old startup famed for its blue cups -- is rapidly expanding in the nation once known more for its oolong and green teas than java, signaling a brewing war between the two coffee chains.

If the young tech-savvy company grows as predicted, it would gain a bigger presence in China than Starbucks to become the nation's No. 1 coffee chain, according to CNN.

"Those blue cups everywhere!" wrote Nanjingmarketinggroup.com on a blog post about Luckin's marketing strategy and growth, last year. 

Starbucks has been heavily focused on growing in China, saying earlier in 2018 that it plans to double its number of shops there to 6,000 from 3,000 by the end of 2022. In December, the company also said it will expand delivery services there by teaming with Ele.me and is partnering with Alibaba for a "virtual" store.

But Luckin has joined forces with Meituan Dianping for delivery services, according to the South China Morning Post. It also has secured hundreds of millions of dollars in investment funding, according to TechCrunch, allowing it to suffer losses while expanding. 

Starbucks didn't immediately respond to an email seeking comment.