Starbucks faces challenges in reviving its business, CEO Brian Niccol said on Tuesday, after the coffee giant posted disappointing global comparable sales and profit with inflation and economic uncertainty driving up costs and dampening U.

Starbucks (SBUX) stock dropped 5.7% Wednesday after the coffee giant's second quarter earnings report disappointed Wall Street and cast a shadow over its CEO's plan to turn around the company. US comparable store sales — a closely watched metric that includes results from stores open for more than a year — fell for the fifth consecutive quarter,