Britain dismissed Iranian threats to close a vital route for the oil trade today as "rhetoric" intended to distract attention from its nuclear programme.
Vice President Mohammad Reza Rahimi has warned that Iran will not allow a "drop of oil" to pass through the Straits of Hormuz if the West widens sanctions against his country.
His warning was underlined by the head of the Iranian navy, Admiral Habibollah Sayyari, who said it would be "really easy" for his forces to block the waterway through which a sixth of the world's oil flows.
The Foreign Office, however, played down the threat, accusing Tehran of trying to deflect attention from its nuclear programme which Western governments fear is being used to develop a nuclear weapon.
"Iranian politicians regularly use this type of rhetoric to distract attention from the real issue, which is the nature of their nuclear programme," a spokesman said.
The Straits of Hormuz link the Gulf oil-producing states of Bahrain, Kuwait, Qatar, Saudi Arabia and the United Arab Emirates with the Indian Ocean. Around 40% of the world's tanker-borne oil passes through them.
The US maintains a naval presence in the Gulf, primarily to ensure the oil routes remain open.
Tensions between Iran and the West have been rising since a report last month by the International Atomic Energy Agency - the world nuclear watchdog - said Iran had carried out tests related to the "development of a nuclear device".
The US announced further economic sanctions while the European Union is also considering fresh measures targeting Iran's oil and financial sectors.
The moves prompted a furious Iranian backlash, with demonstrators storming the British embassy in Tehran, apparently with the backing of the regime.
The Foreign Office spokesman said the Government remained "extremely concerned" at the "possible military dimension" to Iran's nuclear programme.
"We want to find a negotiated solution to this issue and that is why we will continue to pursue a dual track strategy of pressure and engagement until Iranconvinces the international community that it is not pursuing a military nuclear programme," the spokesman said.