US President Donald Trump announced separate probes on Wednesday centred on overproduction and importing goods made with forced labour, targeting China, the European Union, Japan, India and others.

The efforts come weeks after the US Supreme Court struck down his global tariffs, saying he had exceeded his authority in tapping emergency economic powers to impose them on virtually all countries.

China's foreign ministry said on Thursday that "so-called overcapacity is a false proposition".

"China opposes using it as an excuse for political manipulation," ministry spokesman Guo Jiakun told a regular news conference, adding that "tariff and trade wars do not serve the interests of any party".

Others subject to the excess capacity probe initiated Wednesday include Singapore, Switzerland, South Korea, Vietnam, Taiwan and Mexico.

US Trade Representative Jamieson Greer told reporters on Wednesday that the investigations "will focus on economies that we have evidence appear to exhibit structural excess capacity and production in various manufacturing sectors".

He did not specify if the eventual penalties would differ based on the country.

The second probe linked to forced labour will likely be launched "no earlier than tomorrow afternoon" and impact roughly 60 partners, he said.

Trump has in the meantime imposed new 10 percent duties on imports, to last until July 24 while officials work on more durable measures as they resurrect his trade agenda.