Alibaba's digital payment service, Alipay, is set to be released in the US. It is expected that around 4 million businesses will take up the service, which is said to be aimed at Chinese visitors to the country. The move means that Alibaba's payment system will be brought into direct competition with Apple Pay, Android Pay and PayPal. Alipay is one of the most popular digital wallets in China, and has been looking to expand into Western markets over the past few years. Alipay has around 450 million users around the world.