AliExpress, Alibaba Group’s international e-commerce site, is testing a new VIP membership program in some markets, as it tries to attract and retain high-spending customers in a challenge to Amazon, according to a person with direct knowledge of the efforts.

The VIP program, called Elite, is available on an invitation-only basis to customers who have spent more than $800 a year on AliExpress purchases, the person said. The company is piloting the program in Australia, the U.K., Germany and Spain, and plans to bring it to more European markets as well as South Korea next month, they added.