The United States has put China’s third-largest ecommerce platform on its blacklist of “notorious markets” for violations of intellectual property rights, as the world’s two biggest economies are entangled in negotiations to end a tit-for-tat trade war.

The US trade representative’s office added Pinduoduo for the first time to its list of high-profile marketplaces in foreign countries that repeatedly engage in counterfeiting and cause significant financial harm to US businesses.

Pinduoduo, the Tencent-backed Chinese e-commerce group, was set up only three years ago and has reshaped China’s vibrant online shopping industry dominated by Alibaba and JD.com with its group discounts on everything from toilet paper to pot plants, targeting consumers in China’s smaller cities and rural areas.