Google's mobile payment service, Android Pay, is coming to the U.K., marking its first expansion outside the U.S. On Wednesday, Google joins Apple Pay, which launched in the U.K. nearly a year ago. With both services, users merely tap a phone next to a store's payment reader to charge a credit or debit card. But it works only with stores that have newer wireless readers called NFC. Another challenge has been persuading consumers that it's easier than pulling out a plastic card for payment. Apple Pay is also in China, Canada, Australia and Singapore, with Hong Kong and Spain to come. Google says Android Pay will expand to Singapore and Australia this year. Android Pay's expansion comes as Google holds its annual conference for software developers in Mountain View, California.