Iran on Wednesday reinforced its warning to America against keeping a US navy presence in the oil-rich Gulf, adding steel to a threat that Washington had dismissed as a sign of 'weakness' from Tehran.

'Iran will do anything to preserve the security of the Strait of Hormuz' at the entrance to the Gulf, Defence Minister Ahmad Vahidi said, according to the website of Iran's state television.

"The presence of forces from beyond the (Gulf) region has no result but turbulence. We have said the presence of forces from beyond the region in the Persian Gulf is not needed and is harmful," he was quoted as saying.

The comments echoed a warning issued on Tuesday by Iran's military that it would unleash its 'full force' if a US aircraft carrier is redeployed to the Gulf.

"We don't have the intention of repeating our warning, and we warn only once," Brigadier General Ataollah Salehi, Iran's armed forces chief, said as he told Washington to keep its aircraft carrier out of the Gulf.

The White House on Tuesday had brushed off the warning, saying it 'reflects the fact that Iran is in a position of weakness' as it struggles under international sanctions.

The US Defence Department said it would not alter its deployment of warships to the Gulf.

But on Wednesday, Salehi again stressed his warning, and called 10 days of Iranian navy war games just held near the Strait of Hormuz as a 'message' to the United States.

"The forces from beyond the region have received the appropriate message from these manoeuvres," he said, according to the official IRNA news agency.

"Those who have come as enemies should be afraid of our manoeuvres," he said.

The exercises climaxed on Monday with the Iranian navy test-firing three types of missiles designed to sink warships.

The head of Iran's parliamentary national security and foreign policy commission, Aladdin Brujerdi, was also quoted by the Fars news agency as saying the US description of Iran being weak 'is a completely illogical stance'.

He added: "The US talks about sanctioning our oil but they should know that if Iran's oil exports from the Persian Gulf are sanctioned, then no-one will have the right to export oil through the Strait of Hormuz."

The developments have sent the price of oil soaring. New York trading of West Texas Intermediate crude was at $102.60 per barrel, while Brent North Sea crude contracts in London were selling for $111.81.

"The situation with Iran remains worrisome," said Nick Trevethan, a senior commodities strategist at ANZ Research in Asia.

"The consequences of any military action in the Middle East will be enormous. A spike in crude prices will kill off any recovery in the US," he added.

Iran's war games were meant to show the Islamic republic could close the strategic Strait of Hormuz, through which 20 per cent of the world's oil flows, if it is attacked or its oil exports are curbed by sanctions.

Last week, a US aircraft carrier, the USS John C Stennis, passed through the strait and eastward, through the Gulf of Oman and a zone being used by the Iranian navy for its drill.

Iranian military officials said that, if it tried to return through the Strait of Hormuz to the Gulf, it would be attacked.

The US carrier would face the 'full force' of Iran's navy, a navy spokesman, Commodore Mahmoud Mousavi, told Iran's Arabic television service Al-Alam on Tuesday.

The US Defence Department said in a statement it would continue the rotation of its 11 aircraft carriers to the Gulf to support military operations in the region.

"Our transits of the Strait of Hormuz continue to be in compliance with international law, which guarantees our vessels the right of transit passage," it said.

The Pentagon also underlined its pledge to keep the Strait of Hormuz open, saying 'we are committed to protecting maritime freedoms that are the basis for global prosperity; this is one of the main reasons our military forces operate in the region'.

The increasingly tense situation in the Gulf was taking place as Iran struggled with turmoil on its domestic currency market.

Foreign exchange shops on Wednesday were shuttered as traders refused to comply with a central bank order putting a new, low cap on the value of the dollar against the Iranian rial, which has come under intense pressure in recent days.

Iranian authorities were trying to shore up their currency after it slid 12 percent on Monday to a record low against the dollar the day after the United States enacted new sanctions hitting Iran's central bank.

Iran, however, insisted the volatility of the rial is not the result of sanctions.

It 'definitely has nothing to with sanctions', foreign ministry spokesman Ramin Mehmanparast said on Tuesday.

The United States and other Western nations have imposed sanctions on Iran's economy over Tehran's controversial nuclear programme, which they believe is being used to develop atomic weapons.

Iran has repeatedly denied that allegation, saying the programme is purely for energy and medical uses.