China's imports and exports fell more than expected in September, official data showed on Monday, as cooling demand at home and abroad hit trade in the world's second largest economy.

Globally, China's exports dropped 3.2 per cent in September from the same period last year, while imports dived 8.5 per cent, according to data from the customs administration.

The figures were worse than a Bloomberg forecast, which estimated exports to drop 2.8 per cent and imports fall 6.0 per cent.

The European Union has also replaced the United States as China's top trading partner amid a bruising tariffs spat, with imports from the US down 26.4 per cent on-year in September.

China promised to increase US agricultural purchases in a partial US-China deal announced on Friday, which also includes protections for intellectual property and opening up financial markets.

Engulfed in an impeachment inquiry, US President Donald Trump heralded the deal as a major breakthrough.

But the deal may only offer a temporary tariff reprieve because it lacks specifics and leaves the thorny issues such as unfair state subsidies to Chinese firms for later, analysts told AFP.

So far, the two sides have imposed punitive tariffs covering more than $360 billion worth of goods in two-way trade.

China's trade surplus with the US narrowed 3.9 per cent to $25.8 billion in September from $26.9 billion in August.

"The mini US-China trade deal reached on Friday doesn't alter the outlook significantly," said Martin Lynge Rasmussen, China economist at consultancy Capital Economics.

"Looking ahead, exports look set to remain subdued in the coming quarters," he wrote in a research note. China's total trade surplus in September was $39.65 billion.