China warned the Trump administration on Tuesday against reigniting trade tension by restoring tariffs on its goods next month, and threatened to retaliate against nations that strike deals with the United States to cut China out of supply chains.

Its new deal with Vietnam and its fresh tariff threats issued to many other countries seem designed to reduce China’s role in their supply chain. Countries that had hoped to stay out of the new cold war now fear they are being forced to pick a side. To appease the world’s biggest market, they must anger the world’s biggest trader.

President Donald Trump said at least seven countries can expect tariff letters on Wednesday morning, as he ramped up pressure on nations to strike deals with the United States by saying his new August 1 deadline would not be extended.