Google is bringing its mobile payments service, Android Pay, to the U.K.

The tech giant said Wednesday that it would expand its mobile payment service to the U.K., joining two other existing markets, the U.S. and Australia.

The move is a major step forward for the fledgling digital wallet in its battle with rival Apple Pay, which has a big head start with availability in the UK, Canada, Australia, and China.

Android Pay, which debuted in September, lets shoppers pay at store checkout counters by waving their Android smartphones in front of a wireless reader. In December, Google said the service would arrive overseas for the first time in Australia in early 2016.

Google said Wednesday that “millions” of U.S. retail stores already have point-of-sale registers that accept Android Pay, which relies on near field communications technology, or NFC. Shoppers upload their credit and debit card information to the mobile app to pay instead of using cash or taking credit cards from their wallets.

Google also touted that Android Pay is getting 1.5 million new registrations each month.

In the UK, Android Pay will support MasterCard ma and Visa v credit and debit cards from a number of local financial institutions including Bank of Scotland, First Direct, Halifax, HSBC, and Lloyds Bank.

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Stores that will accept Android Pay include Boots, Starbucks, BP, Costa Coffee, and Waitrose. Similar to Apple’s rival service, Apple Pay, users can also tap and pay on public transportation such as the Tube, buses and trains in London.

Apple Pay, which is a similar payments service for iPhones and Apple Watches, has a nearly one year head start in the U.K. But for Google, the U.K. could be a massive market in the company’s bid to take a piece of the mobile payments pie. According to reports, 54.2% of mobile phones sold in the country during the first quarter of 2015 were Android devices.

Contactless payments are also on the rise in the country. Last year, British shoppers made nearly 1 billion so-called “contactless” purchases in stores and elsewhere including in the London Underground Tube.