(Reuters) -Starbucks on Tuesday reported a surprise drop in second-quarter comparable sales, as it battled weak demand for its coffees in the United States and China, its two biggest markets.

With demand falling across the board, Starbucks reported a fall in same-store sales for the first time in nearly three years, sending its shares down 8% in extended trading.

“In a highly challenged environment, this quarter’s results do not reflect the power of our brand,” CEO Laxman Narasimhan said.

Demand in the United States decelerated for a second straight quarter as boycott movements impacted traffic at its stores, while a choppy macro environment weighed on demand for its pricier beverages.

Although the company is working on solidifying its position in the premium coffee market in China, it still grapples with increased competition from mass-market brands, which offer coffee that is easier on the pocket for cautious consumers.

The coffee chain’s second-quarter global comparable sales fell 4%, compared with a 1.44% rise expected on average by analysts, according to LSEG data.

Comparable sales in China fell 11%, compared with a 10% jump in the preceding quarter, while in the United States, they fell 3%.

(Reporting by Juveria Tabassum; Editing by Anil D’Silva)