China's Taobao and Yahoo Japan announced a partnership Monday that will open their online markets to consumers of both countries.

Taobao, China's e-commerce website, is teaming up with Yahoo Japan to allow merchants on their retail sites to sell in each other's markets, broadening consumer choices.

When the service begins in June, it could create the largest online shopping market in the world, offering 450 million products to 250 million users.

"We are pleased to help Japanese small businesses sell their products to China on our Taobao platform," said Jack Ma, chairman and CEO of Alibaba Group, which owns Taobao. "Meanwhile, our respective customers will eventually be able to choose from millions of products from China and Japan."

The cooperation is the first indication of Taobao's ambitions to expand overseas. Yahoo Japan, owned by SoftBank Corp., is the largest Internet company in Japan and accounts for a huge share of the country's auction market.

"We expect that the Asian economy will continue to develop further, led mainly by China and Japan, and that e-commerce business will be the core of that growth," said Masayoshi Son, chairman and CEO of SoftBank Corp.

"The new platforms we launch in June will be the optimal choice for all small businesses to engage in cross-border e-commerce, and make cross-border shopping environments possible for customers as they do business as usual. Through this partnership, we want to contribute to Asia's economic growth."