Analysts said last month's strong export growth - which might indicate USA tariffs are not biting much yet - is unlikely to be sustained.
The US Energy Department said it would make it more hard to ship nuclear technology to China, one of the few growing markets for new plants as the Asian economy tries to meet rising electricity demand through low-carbon sources.
Chinese exports to the United States have at least temporarily defied forecasts they would weaken after being hit by punitive tariffs of up to 25 percent in a fight over American complaints about Beijing's technology policy.
China has responded by imposing counter tariffs, which the Trump administration alleges show political interference by targeting products from key states in next month's congressional elections.
In fact, the September surplus with the USA was larger than China's overall trade surplus of $31.69 billion for the month.
Analysts say a sharp depreciation of the yuan has also helped China weather the tariffs by making its exports cheaper.
"The big picture is the Chinese exports have so far held up well in the face of escalating trade tensions and cooling global growth, most likely thanks to the competitiveness boost provided by a weaker renminbi", said Julian Evans-Pritchard, senior China economist at Capital Economics.
It was about $196.01 billion in the same period a year ago.
Along with electrical machinery, exports for textiles, furniture and chips all rose faster than in the previous month, the customs data showed.
The two countries already exchanged tariffs on $50 billion worth of each other's goods earlier this year.
Trump said the Chinese want to negotiate but he does not believe they are ready and he told them so.
China's September exports rose a solid 14.5 percent from a year earlier, well above expectations despite wider application of US tariffs and signs of shrinking export orders for Chinese companies.
The trade war entered a new level in September, with the U.S. imposing 10 per cent tariffs on US$200 billion worth of goods imported from China, effective as of September 24, which could escalate to 25 per cent in January 2019, while China fought back with tiered tariffs from 5 to 10 per cent on US$60 billion of U.S. goods.
Iron ore imports rose to their highest level in four months as steel mills ramped up output ahead of winter production restrictions.
While the data showed China's trade remained strong for the month, analysts forecast the trade war will begin to hurt in the coming months.
To shore up growth, Beijing has pledged to increase export tax rebates from November 1 for the second time this year and promised to cut corporate burden on a larger scale to help struggling Chinese firms.
The International Monetary Fund this week cited the trade war as it lowered its 2019 growth forecast for China, which is set to see its slowest expansion since 1990.
China will cut import tariffs on a wide range of goods beginning on November 1, as part of Beijing's pledge to take steps to increase imports this year amid rising tension.