The second round of tariffs that the Trump administration imposed on China came into effect only on September 24, so the increase in exports last month might have been the result of Chinese companies rushing to sell their products before the additional duties were added.
That surplus widened to a record $34.1 billion in September as exports to the American market rose 13 percent from a year earlier to $46.7 billion, down slightly from August's 13.4 percent growth.
These efforts are necessary to strike an appropriate balance between the long-term risk to US national security and economic interests, as well as the immediate impact to the US nuclear industrial base, the US' Department of Energy said.
The U.S. equities turbulence roiled through Asian markets early on Thursday, with the benchmarks from Tokyo to Hong Kong seeing declines in excess of 3 percent.
Mnuchin did not report any breakthroughs in his discussions with the Chinese but he indicated that Trump may meet with Chinese President Xi Jinping during a summit of leaders of the Group of 20 biggest global economies in Argentina in late November.
"We've been very clear with China that we need to have structural changes, that we need a reciprocal trading relationship and we should be able to increase our exports by hundreds of billions of dollars", he said.
Beijing's exports to the United States have at least temporarily defied forecasts they would weaken after being hit by punitive US tariffs of up to 25 per cent. In the past two years, China has failed on only one criteria, its high trade surplus with the United States.
Chinese exporters of lower-value goods such as handbags and surgical gloves say USA orders have fallen off. The tariffs are set to rise to 25 percent in January if the trade dispute is not resolved by then, and Trump has vowed to impose tariffs on the remaining $267 billion worth of Chinese imports.More news: DUP steps up warning to May not to compromise on Border
Iron ore imports rose to their highest level in four months as steel mills ramped up output ahead of winter production restrictions.
The U.S. Treasury chief and People's Bank of China Governor Yi Gang extensively discussed currency issues on the sidelines of the International Monetary Fund and World Bank annual meetings on the Indonesian resort island of Bali.
Growth in China's factory sector in September stalled after 15 months of expansion, with export orders falling the most in more than two years, a private business survey showed.
S&P expects China's gross domestic product to grow at a 6.5 per cent rate this year, 6.3 per cent next year and 6.1 per cent in 2020.
The government is also concerned about diversion for use of technology by other countries, one of the officials said.
Shipping containers are seen at a port in Lianyungang, Jiangsu province, China September 8, 2018.
China will cut import tariffs on a wide range of goods beginning on Nov 1, as part of Beijing's pledge to take steps to increase imports this year amid rising tension.