TEHRAN - A senior Iranian Revolutionary Guards commander said on Thursday the United States was not in a position to tell Tehran "what to do in the Strait of Hormuz", state television reported, after the US said it would preserve oil shipments in the Gulf.

Tehran's threat to block traffic through the crucial passage for Middle Eastern crude suppliers followed the European Union's decision to tighten sanctions on Iran over its nuclear programme, as well as accompanying moves by the United States to tighten unilateral sanctions.

A US naval ship is pictured during the Velayat-90 war game on the Sea of Oman, near the Strait of Hormuz in southern Iran. A senior Iranian Revolutionary Guards commander said on Thursday that the US was not in a position to tell Tehran "what to do in the Strait of Hormuz", state television reported. [Photo/Agencies]

Iran's English-language Press TV quoted Hossein Salami as saying: "Any threat will be responded by threat ... We will not relinquish our strategic moves if Iran's vital interests are undermined by any means."

Separately, Salami was quoted as saying by the official IRNA news agency: "Americans are not in a position whether to allow Iran to close off the Strait of Hormuz."

The US Fifth Fleet said on Wednesday it would not allow any disruption to shipping in the Strait of Hormuz, a strip of water separating Oman and Iran.  

At loggerheads with the West over its nuclear programme, Iran said earlier it would stop the flow of oil through the strait if sanctions were imposed on its crude exports.

The Iranian threat pushed up international oil prices on Tuesday although they slipped back on Wednesday in thin trade.

Analysts say that Iran could potentially cause havoc in the Strait of Hormuz which connects the biggest Gulf oil producers, including Saudi Arabia, with the Gulf of Oman and the Arabian Sea. At its narrowest point, it is 21 miles (34 km) across.

But its navy would be no match for the firepower of the Fifth Fleet which consists of 20-plus ships supported by combat aircraft, with 15,000 people afloat and another 1,000 ashore.  

This is not the first time the Iranians have threatened to disrupt the oil flow in the Gulf, including in 2008 and 2010 when Iran talked about shutting the Strait as retaliation for any military strike on the country's nuclear sites.

Neither the United States nor Israel have ruled out military action if diplomacy fails to resolve a long-running dispute over Tehran's nuclear ambitions.

Israel, widely believed to have the Middle East's only atomic arsenal, has described Iran's nuclear programme as a threat to its existence. Iran refuses to recognise Israel.  

Tehran says it needs nuclear technology to generate electricity. Iran has been hit by foreign sanctions, including four rounds of UN sanctions, over its refusal to halt its sensitive nuclear work.  

To show off its military capabilities, Iran launched a 10-day large-scale naval wargames in the Gulf on Saturday.

Iran's state television reported on Thursday the country's surveillance plane filmed a US aircraft carrier during the drill.  

"We have filmed and photographed a US aircraft carrier as it was entering the Gulf of Oman," said Iran's Navy Chief Habibollah Sayyari. "The area is under our full control."