Nearly four years after launching a simplified-Chinese version of its App Store, Apple has added UnionPay as a payment option for App Store customers in China.

"The ability to buy apps and make purchases using UnionPay cards has been one of the most requested features from our customers in China", said Eddy Cue, Apple's senior vice president of Internet Software and Services. "China is already our second largest market for app downloads, and now we're providing users with an incredibly convenient way to purchase their favorite apps with just one-tap".

China UnionPay, a bankcard network approved by China's State Council and the People's Bank of China, is the only domestic issuer of cards in China, with acceptance in over 140 countries and regions and issuance in over 30 countries. The UnionPay network has been extended to all cities and rural areas in China, Apple said.

Apple recently launched its own mobile payment system dubbed Apple Pay, but it isn't yet officially available outside the US, although you can trick it to work internationally. During his recent visit to China, Apple chief Tim Cook said that bringing Apple Pay to the Asian country is on top of the priority list, and he is still seeking to understand the necessary steps to do so.

The news also comes a few weeks after there were reports that Alipay, a Paypal-like service once owned by e-commerce giant Alibaba, and Apple Pay may consider entering into a partnership.

With an estimated 100 million iPhone users, China is clearly an important market for Apple. In its most recent fourth quarter earnings report, the Cupertino-based company said that Greater China generated over $29.8 billion in net sales, up 17 percent year-on-year.