Everyone is angling to work with China UnionPay, the government monopoly card that is the only interbank card network in the country — but MasterCard CEO Ajay Banga said today that his company is winning “90-plus%” of the business.

China UnionPay has issued more than 2.3 billion cards in circulation. Yes, billion with a B.

He said today, per Seeking Alpha:

Jim Schneider – Goldman Sachs

Understanding that it’s very early days with respect to China and there are still a lot of details to understand. Can you maybe share with us your approach to the overall Chinese market and how that might differ from other geographies specifically the existence of UnionPay and new entrants likely Alipay in that market and how you might plan to attack the market generally speaking from a top-level perspective?

Ajay Banga – President and CEO

So over the last couple of years, what we have done there … is that before this whole announcement, we were allowed to do … no domestic processing, but we were clearly the cobranded card … with China UnionPay, so that when Chinese traveled overseas they could use their cards. Over the last few years all the new co-brand cards that were being announced, I think we were the winner and the overwhelming majority of them — I am talking 90 plus percent of those deals over the last two years. And that helped us a great deal in terms of changing our market share on the ground on cards issued in China, where the flow of new cards issued was all coming our way when they were co-brand.

In the meanwhile China UnionPay both operates in China and also have begun to strike over the last many years bilateral deals for acceptance outside of China. The impact of those depends on the marketplace, whether it’s Hong Kong — they’re obviously stronger there — [or] if it’s the United States [where they are] way weaker. And so in addition to the fact that we had to compete on the ground in China, you have to be thoughtful about what is going on with these bilateral acceptance deals. And we went and struck partnerships with China UnionPay to help them where they are expanding some acceptance in return for expanding our acceptance in China.

The announcement Banga referred to is a ruling that may open China up to credit cards beyond UnionPay cards. But the changes will be slow. You can bet Visa, MasterCard and American Express have their applications polished and ready to go.

Another important development regarding China UnionPay is the Palo Alto-based startup Aurfy, formerly known as Comconn. Aurfy offers payment processing for UnionPay cards for U.S. merchants, which opens up the Chinese market to those merchants. Which is a good thing, to say the least.

UnionPay is partnering up these days. It signed a memorandum of understanding with American Express today “that calls for both to explore the expansion of their cooperative activities,” and has worked with Discover since 2005. Additionally, several large U.S. banks, including Wells Fargo and Citibank, have cut deals to allow UnionPay cards access to their ATMs.

Ah, the allure of China.