His concern is trans-shipment, the US charge that China is avoiding tariffs by routing its production through South East Asia. Already Vietnam, according to President Trump, will pay 40% - double the new tariff rate - on goods the US judges to be trans-shipped.

The US set a 19% levy on imports from Thailand and Cambodia, lower than the 36% they originally faced, after President Donald Trump threatened to block trade deals with them unless they ended a deadly border clash.

Senior officials from both countries said they were still waiting to hear final details on the deals after comments by the U.S. commerce secretary, Howard Lutnick.