The longstanding trade war between the United States and China has expanded to the world's shipping lanes, as both nations began imposing significant new port fees on each other's vessels on Tuesday.

The move marks a new front in the economic conflict, directly targeting the maritime industry that forms the backbone of global trade. The U.S. initiated the measures, with the Biden administration announcing the fees earlier this year following a review that concluded China's dominance in shipbuilding, logistics, and maritime sectors was built on "unfair policies and practices."

In a reciprocal response, Beijing announced its own set of fees last week, formalizing a tit-for-tat escalation.

The Chinese regulations, as reported by state broadcaster CCTV, will levy special charges on ships that are U.S.-owned, U.S.-operated, U.S-built, or sail under the U.S. flag. However, the policy includes key exemptions: vessels built in China will be spared the fees, as will empty U.S. ships heading to Chinese shipyards for repairs.

According to the announcement, the extra fees will be collected either at the first port of entry for a single voyage or for the first five voyages within a year, with the billing cycle having commenced on April 17.

The U.S. investigation that prompted its own fees, launched under President Joe Biden, argued that China's market dominance did not result from fair competition. Analysts suggest that Chinese state-owned shipping giant COSCO is likely to be the most severely impacted by the American fees, with projected costs reaching $3.2 billion by 2026.

The new port fees are part of a rapid and severe re-escalation of trade tensions. The situation intensified further on Friday when former President Donald Trump, campaigning for a return to the White House, threatened to impose 100% tariffs on all goods from China if elected. He cited China's reduction in exports of critical minerals as the reason for the proposed measure.

Adding to the pressure, Trump also threatened to enact export controls on "any and all critical software" by November 1.