Jeff Bezos is testing the patience of investors after Inc. missed analysts’ estimates for a second straight quarter, sending the shares tumbling 10 percent.

The world’s largest online retailer yesterday reported a second-quarter loss of $126 million, more than double what was predicted, even as sales climbed 23 percent to $19.3 billion. Expenses jumped 24 percent to $19.4 billion.

Amazon remains one of the most highly valued companies in the U.S., yet the business is losing some of its sheen as profits are dragged down by investments that Bezos, the co- founder and chief executive officer, is making in cloud computing, warehouses and gadgets such as the new Fire smartphone. While shareholders have been patient, they’re increasingly seeking signs that the long-term strategy will work.

“All of us understand making investments, and then there’s a point where investors don’t know what the payoff is,” said Michael Pachter, an analyst at Wedbush Securities Inc. in Los Angeles, who predicted that Amazon would report a quarterly loss. “What if they get to $200 billion in revenue and still don’t have profit?”

For years, shareholders have backed Bezos’s view that big investments are necessary to gain share because Amazon’s business opportunity is enormous and will pay off in the long run. In the process, the company has upended industries from bookstores and traditional retail outlets, to providers of Web- computing software.

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Investors have rewarded Amazon with the highest valuation in the Standard & Poor’s 500 Index, currently trading at 569 times earnings. After climbing 59 percent in 2013, the shares of Seattle-based Amazon have declined 10 percent this year, underscoring investors’ trepidation about mounting expenses.

The stock declined 10 percent to $321.25 as of 8:02 a.m. New York time in early trading.

As Bezos has funneled more money to expanding distribution, grocery delivery services and smartphones and tablets, there’s little sign sizable profits are coming and Amazon issued a forecast yesterday for a wider loss in the third quarter.

“As long as there is money to pour into the business, they will be pouring money into the business,” said Sucharita Mulpuru, an analyst at Forrester Research in Cambridge, Massachusetts.