USTR, which filed the request under World Trade Organization rules, said "a number of U.S. businesses" have raised concerns about disruptions of their websites in China.

"While the United States believes that the best Internet policy is to encourage the free flow of information globally, the United States' WTO request relates specifically to the commercial and trade impact of the Internet disruptions," USTR said in a press release. "Accordingly, the United States is asking China to provide details that will allow a fuller understanding of the legal and policy rules relevant to the accessibility of commercial websites in China."

Websites of businesses based in the U.S. and other countries are "sometimes inaccessible" in China, causing problems for the companies as they try to do business in the country, the USTR said. "The United States would like to better understand China's rules governing website blocking so that service suppliers based outside of China may adopt appropriate policies to avoid encountering this problem," the USTR said.

A spokesman for the Chinese Embassy in Washington, D.C., didn't immediately respond to a request for comments on the USTR's request.

The Computer and Communications Industry Association, a U.S. tech trade group, praised U.S. Trade Representative Ron Kirk for submitting the questions to China.