Amazon.com Inc. is facing a setback in its efforts to modernize brick-and-mortar retail as technical glitches delay the opening of its first cashierless convenience store.

Amazon Go was due to open to the public by the end of this month, after launching in beta mode to employees in December, according to people familiar with the matter. It is unclear when it will now open, as the company works out kinks in the technology to automatically charge customers when they leave, instead of using cash registers, checkouts and lines.

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