China filed a World Trade Organisation complaint on Wednesday against US President Donald Trump's new 10 percent tariff on Chinese imports and his cancellation of a duty-free exemption for low-value packages, arguing the actions are "protectionist" and break WTO rules.

Beijing's request for US trade consultations came as confusion reigned among shippers and retailers over Trump's cancellation of the "de minimis" exemption for package imports valued under US$800.

The tax exemption has benefitted e-commerce firms including Shein, Temu and Amazon.

A US Customs and Border Protection official said all small packages from mainland China and Hong Kong needed to have customs entries on file prior to arrival, and there was the potential for some cargo to be sent back without this paperwork.

RTHK's Washington correspondent, Simon Marks, said this could lead to significant delays in package deliveries.

"So recipients are going to be told in order for you to receive delivery of this package, before you get it, you have to pay the duty, and that will then release the package from Customs," he told RTHK's Hong Kong Today programme.

"This is absolutely going to delay substantially, at least to begin with, the delivery of these items here in the United States, because the customer service is going to have to look at every single one of them - and there are a vast number of them."

Marks warned that apart from the supply chain disruption, consumers will also feel the pinch.

"[Businesses] either have to absorb the tariffs, or they have to raise the price of the good that they are bringing in from outside the country and providing to American consumers," he explained.

"And that's why so many economists here have argued that President Donald Trump and members of his economic inner circle simply don't understand the costs of tariffs to the American consumers, that they are inherently inflationary."

The WTO said China submitted a request for consultations with the US on the tariffs.

The request for consultations is the start of a dispute process that could lead to a ruling that Trump's duties violated trade rules in the same manner that a 2020 WTO ruling found that his first-term China tariffs broke trade regulations.

But such a victory would be unlikely to bring Beijing relief because the WTO's Appellate Body has been largely inoperable for years, as the US has blocked the appointment of appellate judges over what it views as judicial overreach by the body.

The body is unable to function with fewer than three judges. (Additional reporting by Reuters)