Chinese spies are aggressively stealing secrets to build up China's military and economic power, a US advisory panel on US-China relations has warned.
Its members urged the US Congress to ensure the country was adequately protected against Chinese spying.
The report was published in the same week that US President Barack Obama made his first official visit to China.
A Chinese embassy spokesman in Washington dismissed the allegations as baseless and irresponsible.
The report - which says China's spying is becoming more intense and sophisticated - was produced by the US-China Economic and Security Review Commission.
"China is changing the way that espionage is being done," said Carolyn Bartholomew, who chaired the commission.