Chinese stocks closed lower on Wednesday following two days of mixed endings as investors express worry about trade uncertainties with the US.

The Shanghai Composite Index, the main gauge of Chinese stocks, fell marginally by 1.22 points to 3,503.78. The Shenzhen Component Index slipped 0.2% or by 23.75 points to 10,720.81.

US President Donald Trump said his country would be battling China "in a very friendly fashion," Reuters reported Wednesday. Trump made the remarks after signing a trade agreement with Indonesia.

"In our base case, we assume that the U.S. tariff rate on China would stay unchanged at 30% - but the recent escalation of U.S. tariffs on other economies is likely to further dampen global trade momentum," Reuters quoted Morgan Stanley analysts as saying on Wednesday.

China's export performance could hang in the balance after the US started introducing a dual-level tariff structure on Vietnamese imports: 20% for direct imports and 40% for what the US deems as Chinese transshipments, Reuters reported, citing the analysts.

In the corporate front, Smartsens Technology (SHA:688213) forecast a surge of up to 180% in first-half profit following higher shipments of 50-megapixel smartphone sensors. Shares in the eCMOS image sensor chip designer closed 5% lower.