US has 'grave concerns' with Chinese trade secret theft

"In practice, remedies under Chinese law are difficult to obtain," the agency said.

Earlier this year, the security firm Mandiant released a report detailing evidence that an elite military unit of Chinese hackers has been continuously spying on U.S. companies and government agencies.

The White House has urged China to take "serious steps" to stop the hacking. The administration has not directly accused the Chinese government of launching the attacks on U.S. computer systems, only noting that the attacks are coming from inside the country.

Also in Wednesday's report, the U.S. Trade Representative designated Ukraine as a "priority foreign country" due to the "severe deterioration" of intellectual property protection. The report accused Ukrainian government agencies of "widespread" use of illegal software and said the country has done little to crack down on online copyright infringement.

It is the first time in seven years that a country has received the designation, which is reserved for the most egregious violations. 

In a statement, Acting U.S. Trade Representative Demetrios Marantis called upon Ukraine to "reverse recent backsliding and swiftly resolve the problems."

Barbados, Bulgaria, Paraguay, and Trinidad and Tobago were added to agency's "watch list." Canada moved from the "priority watch list" down to the "watch list" due to improvements in intellectual property protection.

"I hope that Canada will sustain and build upon that progress, and that other listed countries will make similar progress,” Marantis said.