Starbucks President and Chief Executive Officer Kevin Johnson is pictured at the Annual Meeting of Shareholders in Seattle, Washington on March 20, 2019.

Starbucks on Tuesday reported quarterly earnings that beat analysts' expectations, but investors focused on its warning that the Wuhan coronavirus outbreak could deal a blow to its fiscal 2020 outlook.

Shares of the company fell less than 1% in extended trading.

The coffee chain said it has closed more than half of its Chinese locations but expects that it will be temporary.

"The magnitude of the impact will depend on the duration of store closures as we work with local authorities to manage the situation and protect our partners and customers," Chief Financial Officer Pat Grismer told analysts.

The company had planned to raise certain aspects of its forecast but decided against it once the virus started to spread, forcing store closures.

Here's what the company reported compared with what Wall Street was expecting, based on a survey of analysts by Refinitiv:

Earnings per share: 79 cents, adjusted, vs. 76 cents expected

Revenue: $7.1 billion vs. $7.1 billion expected

Global same-store sales: 5% vs. 4.4% expected

Starbucks reaffirmed its fiscal 2020 forecast but said it was excluding the impact of coronavirus. Under its current forecast, its fiscal 2020 revenue is expected to rise between 6% and 8% and global same-store sales growth will be in a range of 3% to 4%.

"The company will update its guidance for fiscal 2020 when we can reasonably estimate the impact of the coronavirus," Starbucks said in the earnings release.

The company also said that it expects that the virus will "materially affect" its results for the fiscal second quarter and fiscal 2020. Executives said that Chinese locations that are still open have seen sales slow down, compared to historical numbers.

Grismer said that the latest it would update its forecast would be April 28, when the company announces its fiscal second-quarter results. China accounted for 10% of Starbucks' revenue during its first quarter.

The concerns over the spreading outbreak overshadowed a solid fiscal first quarter that included one of its strongest holiday seasons ever.

The global coffee chain reported fiscal first-quarter net income of $885.7 million, or 74 cents per share, up from $760.6 million, or 61 cents per share, a year earlier.

Excluding the impact of restructuring and impairment costs and other items, the global coffee chain earned 79 cents per share, topping the 76 cents per share expected by analysts surveyed by Refinitiv.

Net sales rose 7% to $7.1 billion, meeting expectations. U.S. same-store sales increased by 6%, boosted by more customers visiting its cafes. The company attributed the traffic bump to the popularity of new cold drinks, like the Pumpkin Cream Cold Brew and the Irish Cream Cold Brew, timed for the holiday season.

Chief Operating Officer Roz Brewer said that the chain will introduce a sandwich with a meatless patty in the U.S. and Canada later this year. A week ago, Starbucks shared its long-term goal of becoming "resource positive," meaning that it would store more carbon than it emits, eliminate waste and provide more freshwater than it uses. Part of its plan to reach such an ambitious goal includes adding more plant-based menu options.

About 1.4 million U.S. customers joined Starbucks' loyalty program, up 16% from a year ago. Starbucks Rewards now counts 18.9 million Americans as active members.

Sales at Chinese locations open at least a year increased by 3% as Starbucks faces greater competition. Chinese rival Luckin Coffee, which recently surpassed Starbucks as the largest coffee chain in China, has been putting pressure on business in Starbucks' second-largest market. Starbucks expects to add 2,000 net new locations worldwide in fiscal 2020.

Mobile orders in China accounted for 15% of China's total revenue, up 10% from the previous quarter. Delivery accounts for 9% of those sales. Starbucks has a delivery partnership with e-commerce giant Alibaba in China, where beverage delivery is more popular than in the U.S.

The first coronavirus patient was flagged on Dec. 31. Since then, the virus has spread rapidly, with more than 4,600 confirmed cases worldwide, with the majority concentrated in mainland China. Global health authorities are still working out how to best contain the deadly virus, making it difficult for companies like Starbucks to predict how long it will affect their businesses.

Read the full earnings release here.