The two companies were among 33 websites or public markets in China, Russia, India and other countries that the US Trade Representative's (USTR) office said facilitate trade in music, clothing and other goods that are fake or unauthorised copies.
China is a leading source of fake and counterfeit goods despite repeated government crackdowns. Beijing launched its latest enforcement effort in October and says it hopes to achieve lasting results.
The USTR report said Baidu links to websites that sell pirated or counterfeit goods while outside merchants use Taobao, an e-commerce platform operated by Alibaba Group, to sell infringing items. It said the list was not a legal finding but an effort to call attention to abuses and encourage governments to stop them.
The outlets cited "exemplify the problem of marketplaces dealing in infringing goods and helping to sustain global piracy and counterfeiting," the report said. "The United States urges the responsible authorities to intensify efforts to combat piracy and counterfeiting in these and similar markets."
The report said Taobao is making "significant efforts" to address piracy but "still has a long way to go in order to resolve those problems".