BEIJING, March 26 (Reuters) - The U.S. administration last week sent a letter to Chinese economic overseer Liu He seeking a tariff cut on U.S. autos to help cut China's trade surplus with the United States, the Wall Street Journal said, citing unnamed sources.

In the letter, U.S. Treasury Secretary Steven Mnuchin and U.S. Trade Representative Robert Lighthizer said China should also buy more U.S. semiconductors and give U.S. firms greater access to the Chinese financial sector, the Journal said, quoting sources with knowledge of the matter.

In the past few days, fears of a trade war have mounted following U.S. President Donald Trump announcement on Thursday of plans for tariffs on up to $60 billion of Chinese goods.

Firing a retaliatory warning shot in response to separate U.S. tariffs on steel and aluminium, China declared plans to levy additional duties on up to $3 billion of U.S. imports.

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.

Liu He, one of China's newly appointed vice premiers, told Mnuchin in a telephone call on Saturday that the U.S. has flouted trade rules with its inquiry into intellectual property, and that China will defend its interests.

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. (Reporting by Ryan Woo; Editing by Simon Cameron-Moore)