Pictures of the captive crew show them huddled on the floor as they were gleefully paraded on state TV by Iran.
Stressing that Iran is not after a military confrontation in the region, Rouhani said "Iran will not allow anyone to disrupt the order in the Persian Gulf and the Strait of Hormuz".
During the final days of Theresa May's premiership, Britain has sought to cobble together an as-yet-undefined "Europe-led force" that could protect shipping in the waterway, which transports one-fifth of the world's crude oil supply.
The Stena Impero was seized by Iranian forces Friday while transiting the vital Strait of Hormuz - providing the first test for Johnson on becoming prime minister Wednesday afternoon.
Deputy Foreign Minister Abbas Araqchi is visiting Paris to convey Rouhani's message to Macron, the conservative Iranian website Alef quoted "an informed source" as saying. A German Foreign Ministry spokesman said Berlin was talking to Britain and France about the idea. He singled out the United Arab Emirates for criticism, saying it had become a base for attacks on Iran, and repeated earlier Iranian threats to attack all USA targets in the region in the event of war.
Iraqi Prime Minister Adel Abdul Mahdi was visiting Tehran on Monday, where Iran's President Hassan Rouhani said, "Iran has been, and will be, the main guardian of security and freedom of navigation in the Persian Gulf, the Strait of Hormuz and the Sea of Oman during history".
He told Express.co.uk: "The precedent here is the one-day war in 1988, when the United States and Iran had a naval conflict for a single day".
US Central Command said it was developing a multinational maritime effort in response to the situation. Spain, Sweden, Poland and Germany also showed interest.
Any mission would still need parliamentary approval in some European Union countries, diplomats said.
US President Donald Trump said at the time he had been prepared to strike three Iranian targets in retaliation but called off the operation at the last minute because such a response would not have been "proportionate".
Tehran has already given up on complying with some of the deal's limits on its nuclear programme in retaliation for the United States withdrawal and what it sees as the failure of other parties to help it circumvent sanctions. "You can see it laying right down on the bottom of that lovely bed of water", the U.S. president said in remarks posted on the White House website.
A USA request for an global mission to protect shipping, aired at a North Atlantic Treaty Organisation defence ministers' meeting in Brussels on 27 June, was resisted by France and Germany. Since then, Washington has reinstated sweeping sanctions against Tehran and has also expanded its military presence in the region.
The president of Iran has signalled a deal could be possible regarding the British-flagged tanker seized in the Strait of Hormuz - if the United Kingdom releases an Iranian oil tanker seized by the Royal Navy off Gibraltar earlier this month.
Taiwan blames China after being stripped of skating event
Washington has no formal ties with democratic Taiwan, but is bound by law to help provide it with the means to defend itself. But the exiled Tibetan Buddhist spiritual leader maintains that he only wants a greater degree of autonomy for the region.
Trump Reaches Budget Deal With Democrats
The last thing he wants is another government shutdown or a debt limit debacle, and the agreement avoids that risk. Legislation to prevent a government shutdown will follow in September.
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