BEIJING/LOS ANGELES — The United States and China on Tuesday began imposing additional port fees on ocean shipping firms, escalating tensions in the ongoing trade conflict between the world’s two largest economies. The levies target vessels transporting everything from crude oil to consumer goods.

China started collecting charges on U.S.-owned, operated, built, or flagged vessels, while exempting Chinese-built ships and empty vessels entering Chinese shipyards for repair. The fees apply either at the first port of entry for a single voyage or for the first five voyages in a year, following an annual billing cycle starting April 17.

The U.S. had earlier announced its own port fees on China-linked vessels to counter Beijing’s influence over global maritime logistics and support U.S. shipbuilding. Analysts estimate China-owned container carrier COSCO could bear nearly half of the expected $3.2 billion cost in 2026.

“This tit-for-tat symmetry locks both economies into a spiral of maritime taxation that risks distorting global freight flows,” said Athens-based Xclusiv Shipbrokers Inc. The measures coincide with U.S. threats of additional tariffs on Chinese exports and potential sanctions against countries backing the UN’s maritime emissions reduction plan, which China supports.

Shares of COSCO rose over 2% in early trading as the company announced a plan to buy back up to 1.5 billion yuan ($210 million) in shares over the next three months to maintain corporate value and protect shareholders.

Experts warn the move signals a shift in shipping from a neutral conduit of global trade to a direct instrument of statecraft.