British and French ships joined a US carrier group in a six-strong flotilla of warships which passed through the sensitive Strait of Hormuz, Britain's Ministry of Defence said Sunday.
The ministry said a Royal Navy frigate, HMS Argyll, was part of a US-led carrier group to sail through the waterway which Iran has threatened to close over Western moves to impose new sanctions over Tehran's nuclear programme.
A spokesman said: "HMS Argyll and a French vessel joined a US carrier group transiting through the Strait of Hormuz, to underline the unwavering international commitment to maintaining rights of passage under international law."
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He said Britain maintained "a constant presence in the region as part of our enduring contribution to Gulf security".
British warships have been patrolling in the Gulf continuously since the 1980s.
The Strait of Hormuz is a key transit route for global oil supplies.
European Union foreign ministers meeting in Brussels on Monday are expected to agree to sanction Iran's central bank and announce an embargo on buying Iranian oil.
The United States, France, Britain and Germany accuse Iran of seeking to build a nuclear bomb, but Tehran says its nuclear drive is peaceful.