They kicked in just after midnight ET, which is noon in Beijing.
The Trump administration contends that China has deployed predatory tactics in a push to overtake US technological dominance.
The tariffs will hurt the American high-tech companies that Trump is trying to protect from intellectual property theft as it becomes increasingly hard for those companies to do business in China, she said.
Beijing insists it's the injured party.
From Air Force One, on his way to a rally in Montana, Trump said the United States is ready to target an additional US$200 billion in Chinese imports - and then US$300 billion more - if Beijing refuses to yield to USA demands and continues to retaliate.
American companies doing business in China are particularly anxious. "These tariffs will do nothing to protect United States jobs, but they will undermine the benefits of tax reform and drive up prices for a wide range of products as diverse as tool sets, batteries, remote controls, flash drives and thermostats".
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Hours before Washington's deadline for the tariffs to take effect, US President Donald Trump upped the ante, warning that the United States may ultimately target over $500 billion worth of Chinese goods, or roughly the total amount of US imports from China a year ago.
"Although uncertainties have clearly increased this year and pose downside risks to growth, the latest batch of timely activity indicators suggests that in the shorter term the global economy is resilient to these worries", Ben May, director of global macro research at Oxford Economics in London, said in a report on Thursday.
The company wants customers to split the cost of the tariff hike, but few are willing, said Tong.
He also upped his threat to go further - saying he'd target up to US$500 billion of Chinese goods if they retaliate.
First "34 (billion dollars), and then you have another 16 in two weeks and then as you know we have $200 billion in abeyance and then after the $200 billion we have $300 billion in abeyance. Ok? So we have 50 plus 200 plus nearly 300", he said.
"More than 70,000 jobs depend on the Port of Oakland".
US companies had US$256 billion in investment in China by the end of past year, exceeding China's US$140 billion in the United States, according to a report by the National Committee of US-China Relations and Rhodium Group in April.
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American farmers and manufacturers, in particular, seem poised to bear the brunt of the effects of the U.S.
And if Trump extends the tariffs to $550 billion in Chinese imports, there's no way consumers could avoid being caught in the crossfire: The taxes would have to hit consumer products like televisions and cellphones.
Duties imposed by the U.S. would trigger "trade diversion" from other steel makers, who would then dump their products in India, said Bhaskar Chatterjee, secretary general at Indian Steel Association.
The US president said America might target Chinese goods worth $500bn - the total value of Chinese imports in 2017.
I view these tariffs as a negotiating ploy by President Trump to try to force the Chinese to open up their market better for American companies. "We can expect job losses and a decline in investor and consumer confidence", longtime Beijing-based attorney James Zimmerman tells NPR's Rob Schmitz.
While the Chinese government did not immediately announce reciprocal tariffs on U.S. imports, there are reports that China's General Administration of Customs is delaying clearing United States imports at major Chinese ports.
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