BEIJING—Alibaba Group Holding Ltd. on Tuesday defended itself against accusations by a U.S. clothing trade group that it tolerates fake goods on its Taobao e-commerce platform.

In letters to U.S. securities and trade officials dated last week, the American Apparel and Footwear Association described Taobao as one of the biggest platforms for counterfeit goods world-wide. The group urged the regulators to bring up the issue with Alibaba. It said it had spoken with Alibaba about measures to curb counterfeit goods, but implementation...