China will take 'all appropriate measures' to defend interests: official

China's Ministry of Commerce (MOC) said Monday the country will take "all appropriate measures" to defend its legal interests in response to a U.S. trade investigation that has aroused tension between the world's two largest economies.

Without specifying those measures, an MOC spokesperson said China will keep an eye on the investigation in a statement.

U.S. Trade Representative Robert Lighthizer Friday formally initiated an investigation into China's intellectual property (IP) practices under a rarely used trade law, despite worries about potential harm to China-U.S. trade ties.

Section 301, once heavily used in the 1980s and the early 1990s, allows the United States to unilaterally impose tariffs or other trade restrictions on foreign countries. But the country has rarely used the outdated trade tool since the World Trade Organization (WTO) came into being in 1995.

The spokesperson called the move "irresponsible" as it was based on domestic law and defied WTO rules, and U.S. criticism of China's IP protection was "not objective."

"China is strongly discontented about such unilateral, protectionist practice," said the spokesperson.

Since the historic meeting between the presidents of both countries in April, the two sides have made solid progress, and the launch of the investigation sent a wrong signal to the world, the spokesperson said.

The spokesperson called for the United States to make joint efforts with China to promote economic cooperation under the one-year plan and to strive to obtain bigger results.

"We urge the United States to respect facts, respect wishes from businesses of both countries for cooperation, respect multilateral rules, and act with prudence," the spokesperson said.