Slapping tariffs not a constructive way to solve trade war: China to US

China's foreign minister said Friday tariffs are "not a constructive" way to solve the US trade war after President Donald Trump threatened to hit $300 billion worth of Chinese goods with new duties.

"Slapping on tariffs is definitely not a constructive way to resolve economic and trade frictions, it's not the correct way," Wang Yi said on the sidelines of a meeting of Southeast Asia's top diplomats in Bangkok, according to footage broadcast on a Chinese television station.

US President Donald Trump had announced on Thursday he will hit China with punitive tariffs on another $300 billion in goods, prompting Beijing to warn it was the wrong way to resolve the trade war.

The sudden deterioration meant the world's two largest economies have now erected trade barriers covering virtually all of their $660 billion in annual trade in merchandise - confirming economists' fears and sending shudders through Wall Street.

The 10 per cent duties will take effect September 1, and come on top of the 25 per cent tariffs on $250 billion in imports already in place.

He later raised the possibility he could increase the duties further.

"The 10 per cent is... for a short-term period and then I can always do much more or I can do less, depending on what happens with respect to a deal," Trump said at the White House, adding, "it could be lifted up to well beyond 25 per cent."

China has yet to say whether and how it will retaliate, but it has hinted in recent months that it could restrict exports of rare earths, which are vital to the US tech industry, and it is also working on a blacklist of "unreliable" companies that could target US firms.