China internet regulator says web censorship not a trade barrier

China's online censorship system protects national security and does not discriminate against foreign companies, the country's internet regulator said, after the United States labelled the blocking of websites by Beijing a trade barrier.

The U.S. Trade Representative (USTR) wrote in an annual report that over the past year China's web censorship has worsened, presenting a significant burden to foreign firms and internet users.

China has long operated the world's most sophisticated online censorship mechanism, widely known outside the country as the Great Firewall, though USTR had not listed it as a trade impediment since 2013, whentec Xi Jinping became China's president.

The Cyberspace Administration of China (CAC) said that its online censorship did not target specific countries or violate its trade commitments.

"The aim of the internet security inspection system is to guarantee the security and controllability of information technology products and services, safeguard user information security, and strengthen market and user confidence," CAC said in a fax to Reuters late on Friday.

"China scrupulously abides by World Trade Organisation principles and its accession protocols, protects foreign enterprises' lawful interests according to law, and creates a fair market environment for them," the regulator said.