The cost of shipping is rising as major exporters rush to send goods to the United States ahead of the expected introduction of sweeping global tariffs in July even as major ports warn of a big fall-off in shipments this year.

The Trump administration’s expansive tariff plans, announced on April 2 but later paused for three months, have forced manufacturers and importers to reconsider their supply chains. The constant reworking of those plans – most recently the suggestion of separate levies on semiconductors – has left the world’s ports with little certainty.