The US and China on Tuesday began charging additional port fees on vessels linked with each other's country as a trade war between the world's two largest economies moves to the high seas.

US President Donald Trump's administration announced earlier this year it would be imposing the fees on China-linked ships, prompting the reciprocal move by Beijing announced last week.

What are the port fees?

China has said special charges will be levied on ships that are US-owned, operated, built or flagged but that Chinese-built vessels would be exempted.

Another exemption will be empty ships that are going to Chinese shipyards to be repaired, according to a report by state broadcaster CCTV.

The extra port fees charged by China are to be collected at the first port of entry on a single voyage or for the first five voyages within a year, with the billing cycle starting on April 17.

US probe suggests unfair practices by China

The move by Washington to impose the fees on Chinese-linked shipping came after an investigation by the previous administration of President Joe Biden concluded that China's dominance of the global maritime, logistics and shipbuilding sectors resulted from unfair policies and practices.

Analysts say that China-owned container carrier COSCO is likely to be hardest hit by the new fees, which are expected to cost $3.2 billion (€2.8 billion) in 2026.

The port fees come as the trade war between the US and China escalated further on Friday, with Trump threatening to impose new 100% tariffs on goods from China in return for China cutting its exports of critical minerals.

Trump also threatened to put export controls on "any and all critical software" by November 1. 

Edited by: Wesley Rahn