Trump announced that the U.S. will start to charge 10 per cent tariffs on US$200 billion worth of Chinese products from next Monday, significantly widening the scope of a trade war.
The US had already imposed 25% tariffs on $50bn (£38bn) in Chinese imports.
Trump will "immediately" pursue another $267 billion in tariffs if China retaliates.
At the same time, the official said, the U.S. remains open to negotiations.
China's yuan currency has weakened by about six percent against the United States dollar since mid-June, offsetting the 10 percent tariff rate by a considerable margin.
With the new tariffs, about half of China's imports to the United States are covered by punitive trade measures.
China then confirmed it would retaliate but still traders barely flinched. Chinese officials have suggested that planned talks between trade delegations from both countries will now not go ahead.
The officials said China had been given "chance after chance" to change the trade practices considered unfair to U.S. businesses, but "have remained obdurate". It brings all Chinese imports subject to added tariffs to $250 billion, roughly half of China's shipments to the USA previous year. Beijing counterpunched. It imposed a tax of up to 105 percent on USA chicken feet - a throwaway item in the United States that's considered a delicacy in China.
So far, economists have found no broad negative or positive effect from earlier tariffs imposed on China, and on aluminum and steel imports from several countries.
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"For months, we have urged China to change these unfair practices and give fair and reciprocal treatment to American companies", Trump said in a statement. "I think it's going to work out very well with China", he said.
Amid continued trade tensions with the world's second largest economy, Trump "has not been satisfied with the talks with China on this (and) my guess is announcements will be coming soon", economic advisor Larry Kudlow said earlier Monday on CNBC.
The trade war between America and China has escalated, fuelling fears that the global economy could be dragged down.
The products spared included consumer electronics like smart watches and Bluetooth devices, child safety products such as high chairs, vehicle seats and play pens, and certain health-and-safety products such as bicycle helmets, the officials said.
Sohn said he thinks that China will retaliate against every US tariff and that the back-and-forth sparring will escalate until the U.S.is taxing all Chinese imports - $524 billion past year.
The greenback has risen to a 2.5% 2018 gain in recent months after more than reversing a 4% loss wracked up in the first quarter.
By slapping an extra 10 percent tax now and raising it to 25 percent at the end of the year on thousands of Chinese goods, Trump is forcing Beijing officials to ease off on what he believes are predatory trade practices.
The Office of the US Trade Representative concluded after an investigation that China's tactics range from requiring US and other foreign companies to hand over technology in return for access to the vast Chinese market to outright cyber-theft.
But the adjustments did little to appease technology and retail groups who argued that the tariffs would hit consumers hard.
"We can't do that anymore", Trump said. "Business hates uncertainty. They'd rather have an imperfect trading relationship than this much chaos".
Last year, Southern California ports handled $173bn in Chinese imports, about a third of all goods shipped from China to the US, CNBC reported.