China's President Xi Jinping (L) and US President Donald Trump attend a working session on the first day of the G20 summit in Hamburg, northern Germany, on July 7, 2017.

The United States has flouted trade rules with an inquiry into intellectual property and China will defend its interests, Vice Premier Liu He told U.S. Treasury Secretary Steven Mnuchin in a telephone call on Saturday, Chinese state media reported.

The call between Mnuchin and Liu, a confidante of President Xi Jinping, was the highest-level contact between the two governments since U.S. President Donald Trump announced plans for tariffs on up to $60 billion of Chinese goods on Thursday.

The deepening rift has sent a chill through financial markets and the corporate world as investors predicted dire consequences for the global economy should trade barriers start going up.

Several U.S. chief executives attending a high-profile forum in Beijing on Saturday, including BlackRock Inc's Larry Fink and Apple Inc's Tim Cook, urged restraint.

In his call with Mnuchin, Liu, a Harvard-trained economist, said China still hoped both sides would remain "rational" and work together to keep trade relations stable, the official Xinhua news agency reported.

U.S. officials say an eight-month probe under the 1974 U.S. Trade Act has found that China engages in unfair trade practices by forcing American investors to turn over key technologies to Chinese firms.

However, Liu said the investigation report "violates international trade rules and is beneficial to neither Chinese interests, U.S. interests nor global interests", Xinhua cited him as saying.

In a statement on its website, the office of the U.S. Trade Representative Robert Lighthizer said it had filed a request - at the direction of Trump - for consultations with China at the World Trade Organization to address "discriminatory technology licensing agreements".

China's commerce ministry expressed regret at the filing on Saturday, and said China had taken strong measures to protect the legal rights and interests of both domestic and foreign owners of intellectual property.