They kicked in just after midnight ET, which is noon in Beijing.
The Trump administration has contended that China has deployed predatory tactics in a push to overtake U.S. technological dominance, including cybertheft and requiring USA companies to hand over technology in exchange for access to China's market.
Beijing insists it's the injured party.
A ministry statement said, "the Chinese side promised not to fire the first shot, but to defend the core interests of the country and people, it is forced to make a necessary counterattack".
The negotiations began in August but have stalled over US demands created to discourage investment in Mexico and to shift auto production back to the United States.
This trade war will hit American agricultural exports such as pork and soybean hard, but if President Trump ups the ante, products like televisions and other household goods could also be hit, meaning consumers will face higher prices, Matthew Shay, president of the National Retail Federation, told the Associated Press.
The statement reiterated that China "will unswervingly deepen reform, expand opening up, protect entrepreneurship, strengthen property rights protection, and create a good business environment for global companies in China " - an apparent response to the Trump administration's complaints.
He further said that all the flags being made have "Made in China" tags on them. "Soybean demand is there, and it's really, really big as soybeans go into different channels".
Washington imposed 25 percent tariffs on US$34 billion of Chinese imports, a first step in what could become an accelerating series of tariffs.
Economists say that if the back-and-forth stops there, the overall impact on both economies will be minimal even though some industries will suffer. On Thursday, he suggested the possibility of tariffs on nearly $500 billion more of Chinese goods.
He described the potential escalation to reporters aboard Air Force One: "Thirty-four, 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?"
Alia Bhatt wishes Ranbir Kapoor's mother Neetu on her birthday
In yet another post, the mother (Neetu Kapoor), daughter (Riddhima Kapoor) and grand-daughter (Samara) were seen. "Mum's birthday. In the recent pictures that have come up, Ranbir carries niece Samara on his back and they all pose for a million dollar photo.
"We're now looking at a 25 percent tariff on every single soybean that we try to sell to China", said Kirk Merritt, OSA executive director.
That amount is higher than an earlier threat from Trump to target as much as $450 billion of Chinese exports.
That could bring the total of targeted Chinese goods to US$550 billion - more than the US$506 billion in goods that China shipped to the United States past year.
"I've watched for too many years. how we always end up taking the brunt of most trade deals", he said. "If America is cheap, they go to America".
Trump's decision to trigger a trade war isn't confined to the tit-for-tat exchange with China. USA tariffs on steel and aluminum imports have provoked retaliatory measures against billions of dollars of American exports. Trump has added to the tension by threatening new tariffs on cars. "There should be no doubting Beijing's resolve", the newspaper said.
Consumer Technology Association: "While President Trump says his trade policy is meant to punish China, the numbers show that, in reality, US businesses, workers and consumers will pay the price under this policy", said Sage Chandler, the group's vice president for global trade.
Trump's tariffs on the EU, Canada and Mexico are for as much as 25% on imports of steel and aluminium, which the USA has imposed on grounds of national security.
"We urge the two governments to come back to the negotiation table", said Zarit.
Beijing's taxes hit USA -made aircraft, cars, computer chips, fuel, pork and soybeans.
Analysts say China is unlikely to budge on those plans, which it sees as crucial for developing its huge economy.
Trump started the war but it is unclear how he envisages it ending without China volunteering to both significantly damage its own economy and its leadership suffering humiliation in the process.