By Agence France-Presse
Washington imposed levies on $16 billion in Chinese imports, sparking an immediate retaliation in kind from Beijing, which said it "firmly opposes the tariffs and has no choice but to continue to make the necessary counter-attacks".
China also said the US was "clearly suspected" of violating World Trade Organization rules and that it would file a lawsuit with the group.
It is the second round of such measures after the world's top two economies swapped tariffs on $34 billion of goods in July.
The fresh tariffs came as officials from each side hold their first talks since June aimed at easing a row that has dragged on equities for months. However, observers are cautious about what progress they will make initially.
Stock markets in Asia fluctuated through the day and by the close Tokyo was up 0.2 percent while Shanghai rose 0.4 percent.
Singapore jumped 1.6 percent after a one-day holiday and Seoul gained 0.4 percent but Hong Kong fell 0.5 percent and Wellington was also lower.
Sydney fell 0.3 percent -- and the local dollar shed 0.8 percent -- as Australia's Prime Minister Malcolm Turnbull fights for his political life following a leadership challenge.
The S&P/ASX 200 was also being dragged by a 2.8 percent plunge in Qantas as a jump in the airline's profits was offset by its worries about rising fuel costs.
Investors are keeping tabs on developments in Washington after President Donald Trump's former personal adviser admitted a series of charges including illegal use of election funds.
The US leader's ex-campaign manager was also convicted on several counts including bank and tax fraud.
On currency markets the dollar sprang back to life against the yen, pound and euro as well as most high-yielding units after this week's travails, with Federal Reserve minutes signalling it is ready to lift rates again as the economy continues to improve.
"Many participants suggested that if incoming data continued to support their current economic outlook, it would likely soon be appropriate to take another step," the minutes said.
The greenback had taken a hit this week from Trump's comments criticising the central bank's rate increases and accusing it of not backing his economic plan.
However, the Fed's policy committee pointed to "ongoing trade disagreements and proposed trade measures as an important source of uncertainty and risks".
In addition, most members said "an escalation in international trade disputes was a potentially consequential downside risk for real activity".
Attention now turns to this week's annual central bankers' symposium at Jackson Hole in Wyoming, with investors hoping for some idea about governors' plans in light of the China-US trade row.
In early European trade London and Frankfurt were flat while Paris edged up 0.1 percent.
Key figures around 0810 GMT
Tokyo - Nikkei 225: UP 0.2 percent at 22,410.82 (close)
Hong Kong - Hang Seng: DOWN 0.5 percent at 27,790.46 (close)
Shanghai - Composite: UP 0.4 percent at 2,724.62 (close)
London - FTSE 100: FLAT at 7,571.71
Euro/dollar: DOWN at $1.1560 from $1.1595 at 2100 GMT
Pound/dollar: DOWN at $1.2877 from $1.2914
Dollar/yen: UP at 110.81 yen from 110.60 yen
Oil - West Texas Intermediate: DOWN six cents at $67.80 per barrel
Oil - Brent Crude: DOWN 24 cents at $74.54 per barrel
New York - Dow Jones: DOWN 0.3 percent at 25,733.60 (close)