Similar conditions exist in many factories used by Apple, despite promises that Apple is correcting problems, Li told the committee. Factories used by several other U.S. hardware firms also have bad conditions, he said. An Apple representative didn't immediately respond to a request for comments.

The profits of Apple in one year would pay the wages of the 300,000 employees of Foxconn, a Chinese supplier for Apple, for 110 years, Li said. He called on the committee and U.S. government to put pressure on U.S. companies to help fix worker conditions.

Committee members and other witnesses also called on the U.S. government to put pressure on the Chinese government to better protect workers. While the U.S. government took a hard line against the Communist Party in the old Soviet Union and continues to take a hard line against the Communist Party in Cuba, it works with the Communist leaders in China, said Harry Wu, executive director of the Laogai Research Foundation, a human rights group focused on China.

Wu asked committee members if the U.S. government really wants to improve worker rights in China. "I hope so, I don't think so," he said.

Representatives of the Chinese Embassy in Washington, D.C., did not return a message seeking comment on the hearing.