The top U.S. diplomat says China should make significant economic reforms so it does not continue to be a "problem for the international economy."
In a New York Times newspaper interview, published Friday, Secretary of State Condoleezza Rice says Washington also worries about China's military buildup, human rights practices and religious restrictions.
It is a change of tone for Ms. Rice, who generally casts Sino-American relations in a positive light.
Her comments come just a month before Chinese President Hu Jintao makes his first visit to Washington since taking office in 2003.
He will arrive amid Washington's complaints that China manipulates the value of its currency to make its products unfairly cheap on world markets.
Beijing recently changed the value of its currency slightly, but U.S. critics say the change is not large enough to make trade fair.