US President Donald Trump has abandoned his plan to impose a 20 per cent charge on cargo passing through the Strait of Hormuz, only hours before it was due to take effect, while maintaining a naval blockade of Iranian ports and ordering further attacks on Iran.

Trump announced on Tuesday that he had withdrawn the proposed fee following what he described as “highly productive conversations” with Middle Eastern leaders. He appeared to portray the apparent U-turn not as a retreat but as a negotiated victory, claiming that Gulf Arab states had offered trade and investment commitments in place of the proposed toll.

No details, however, were given about the countries involved, the value of the agreements or when they would take effect.

The decision represented an abrupt reversal of his earlier threat. Trump had declared that the US would become the “guardian” of the Strait of Hormuz and collect a 20 per cent charge on cargo in return for providing security. Five hours before the measure was scheduled to take effect, he conceded that nobody should charge ships for using the international waterway.

Trump’s proposal also contradicted the stated position of his own administration. Last month, the US secretary of state, Marco Rubio, insisted: “No country is allowed to charge tolls or fees on an international waterway.” Rubio said that international law required the Strait of Hormuz to remain free from such charges.