British Foreign Secretary Yvette Cooper will say on Thursday that shipping through the Strait of Hormuz, which carries around a fifth of the world's oil and gas, must be toll-free, countering a push by Iran to control the vital waterway.
Iran has said it wants to charge fees for ships to pass through the Strait of Hormuz. Before the US-Israeli war with Iran, the strait was formally treated as an international waterway.
"The fundamental freedoms of the seas must not be unilaterally withdrawn or sold off to individual bidders. Nor can there be any place for tolls on an international waterway. Freedom of navigation means navigation must be free," Cooper will say in an annual foreign policy speech at Mansion House in London, according to advance extracts.
Cooper will also repeat calls by world leaders for Lebanon to be included in a two-week ceasefire agreed between Iran and the US on Tuesday.
Israel on Wednesday launched its biggest attacks yet on Lebanon, targeting the Iran-backed Hezbollah militia.
(Reporting by Gursimran Kaur in Bengaluru; Editing by Sonali Paul)