Missile proliferation has been a key bone of contention in Sino-US relations in recent years, and Beijing has made repeated assurances that it has introduced new oversight regimes to prevent the trafficking of such technologies.
But Paula DeSutter, assistant Secretary of State for verification and compliance, said in testimony to the US-China Economic and Security Review Commission on Thursday that Beijing had failed to take serious steps requested by Washington.
"We continue to see problems in the proliferant behavior of certain Chinese entities and remain deeply concerned about the Chinese government's often narrow interpretation of nonproliferation commitments and lack of enforcement of nonproliferation regulations," she said.
"The Chinese Government appears to view missile nonproliferation, at least in part, not as a goal in and of itself but as an issue that needs merely to be managed as part of its overall bilateral relationship with the United States," she said.
"China has generally tried to avoid making fundamental changes in its transfer policies by offering the US carefully-worded commitments."
"China does not appear to be enforcing controls at its borders, allowing unauthorized transfers to go undetected.
"Furthermore, it must establish a system of end-use verification checks to ensure that items approved for transfer are not diverted."
China has denied its missile control export regimes are inadequate and says it introduced new procedures to stop illegal transfers in August 2002.
But the State Department has regularly slapped sanctions on Chinese firms and individuals it says are implicated in illegal missile and arms transfers.
In one of the latest US strikes against Chinese military technology firms, the State Department in May sanctioned North China Industries Corporation NORINCO, saying it had helped Iran modernize and expand its missile arsenal.
Both the firm, and Chinese officials denied the accusations.
In a report sent to Congress last April, the CIA said Chinese companies had provided dual-use missile-related items and raw materials to countries such as Iran, Libya, "and to a lesser extent, North Korea" in the first half of last year.
The US-China Economic and Security Review Commission is tasked by Congress with assessing China's role in the proliferation of weapons of mass destruction (WMD) and other weapons.