Almost one million fake electronic parts from China have been found in US military aircraft.
A report by the US Senate Armed Services committee found 1,800 individual cases of counterfeit electronic parts being used in military hardware.
They included thermal weapons sights, mission computers used in high altitude defence missiles, aircraft and helicopters.
SH-60B helicopters and P-8A Poseidon planes were some of those in which fake parts were used.
More than 70% of the parts were eventually traced to China, after passing through a "complex supply chain", often involving multiple vendors.
But after China, the UK was the next largest source for fake electronics followed by Canada, according to the report.
"The committee identified instances in which both countries served as resale points for suspect counterfeit electronic parts," it said.
According to one witness quoted in the report, factories of up to 15,000 people have been set up "for the purpose of counterfeiting".
Failure of any one of these parts could put national security at risk, the report said.
The committee said that the suspect parts put the armed forces "at risk" and called for "aggressive inspection and testing practices" to stamp out the use of counterfeit parts.
"Rather than acknowledging the problem and moving aggressively to shut down counterfeiters, the Chinese government has tried to avoid scrutiny," the report said, while calling for China to clamp down on people openly selling fake electronics.