Washington on Friday launched a formal investigation into China's alleged theft of US intellectual property days after US President Donald Trump urged the American trade representative to consider a probe.

"After consulting with stakeholders and other government agencies, I have determined that these critical issues merit a thorough investigation," US Trade Representative Robert Lighthizer said on Friday, announcing the start of an inquiry concerning intellectual property.

Read more: Can Trump succeed in curbing China's intellectual property 'theft'?

US companies operating in China have long complained about China's failure to protect industrial secrets. However, they have also been reluctant to press hard against Beijing for fear of losing access to China's expansive market.

Even before assuming office, Trump railed against US trade policy with China. He has accused the communist nation of cheating the US economy out of "hundreds of billions of dollars in trade."

"China has been taking out massive amounts of money and wealth from the US in totally one-sided trade, but won't help with North Korea. Nice," Trump said in a sarcastic tweet published in July.

China will 'not sit idle'

Earlier this week, Lighthizer said China's industrial policies have posed a "very serious problem" to the American economy.

Read more: China is US' biggest creditor once again

Beijing has yet to respond to the investigation. However, earlier this week China said it would "not sit idle" if the US took action that undermined trade ties, threatening a strong response with "appropriate measures."

The United States is China's second-largest trading partner following the European Union. In 2016, the US had a trade deficit with China of nearly $310 billion (268.7 billion euros).

ls/sms (AFP, Reuters)