China on Thursday issued a stern new warning that it will be forced to retaliate if the U.S. follows through on a threat to levy new import tariffs, beginning Sept. 1.

China is threatening to retaliate against the latest U.S. tariffs President Donald Trump threatened, according to a release from Xinhua News, a government-run media outlet.

Top U.S. and Chinese trade officials met over the phone Tuesday to try to further negotiations to end the countries’ trade war, said to President Donald Trump, who said the negotiations were “productive” and offered optimism that a conclusion could come soon.

China, in retaliation for new U.S. tariffs, revoked its latest goodwill gesture of exempting some Chinese importers from its own tariffs on U.S. soybeans, but at least one U.S. shipment will get through unscathed, according to U.S. government and industry officials.

President Donald Trump said Thursday he will hit roughly $300 billion worth of Chinese goods — effectively the only goods remaining untaxed in the ongoing trade war — with a 10% tariff on Sept. 1, raising concerns that the recently renewed trade talks are not going well.

The U.S. and China have wrapped up their first round of face-to-face trade negotiations since talks fell apart in May and both sides agreed to meet again in September as President Donald Trump continues to tone down expectations of a quick resolution.