Iran on Wednesday renewed its warning to America against keeping a US naval presence in the oil-rich Gulf, underlining a threat Washington has dismissed as a sign of "weakness."

Meanwhile, diplomats said the European Union was on target to impose a threatened embargo on oil imports from Iran, which France said could come by the end of January and which drew US praise.

"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," Defence Minister Ahmad Vahidi said, according to state television's website.

"The long-term presence of the United States in the region increases insecurity and the possibility of tensions and of confrontation," the deputy chief of Iran's forces, Masoud Jazayeri, said, according to the Revolutionary Guards website.

"As a result ... the United States must leave the region."

Jazayeri noted last week's departure of the aircraft carrier USS John C. Stennis from the Gulf, saying: "Since you've gone, don't come back, otherwise you'll be responsible for any problems."

His comments echoed a Tuesday warning that Iran would unleash its "full force" if a US carrier is redeployed to the Gulf.

"We don't have the intention of repeating our warning, and we warn only once," armed forces chief Brigadier General Ataollah Salehi said.

The White House on Tuesday said the warning "reflects the fact that Iran is in a position of weakness" as it struggles under international sanctions.

The US Defence Department said it would continue rotating its 11 carriers to the Gulf to support regional military operations and keep the Strait of Hormuz open.

"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," it said.

Iran has just finished 10 days of naval exercises near the strategic strait at the entrance of the Gulf, aimed at showing it can control the channel and closing it if necessary. Twenty percent of the world's oil ships through the strait.

On Monday, the exercises saw the test-firing of three types of anti-warship missile.

The head of Iran's parliamentary national security and foreign policy commission, Aladdin Borujerdi, was quoted by Fars news agency as saying Wasington's description of Iran as weak "is a completely illogical stance."

"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," he added.

The developments helped send oil prices soaring, though they pulled back a little on Wednesday.

New York's main contract, West Texas Intermediate (WTI) for February delivery, spiked to $103.74, a level last touched on May 11. The contract fell back to $102.61, down 35 cents from Tuesday's close.

Brent North Sea crude for February jumped to $113.97 per barrel -- its highest since November 14. It later stood at $112.82, up 69 cents from Tuesday.

"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."

In Brussels, diplomats said EU governments had reached preliminary agreement on an oil embargo against Iran and are now debating when it should come into force.

"There is an agreement in principle to forge ahead" with an embargo, a diplomat told AFP, but "there is still a lot of work" to agree on its timing for a foreign ministers' meeting on January 30.

The EU had been divided over an oil ban, but reached a breakthrough in late December after Greece, Spain and other nations that buy Iranian crude lifted their objections.

Speaking of the January 30 meeting, French Foreign Minister Alain Juppe said in Lisbon: "It's at this occasion I hope that we can adopt this embargo on Iranian oil exports."

"We have to reassure some of our European partners who purchase Iranian oil. We have to provide them with alternative solutions. But these alternative solutions exist and I think we can attain the objective by the end of January."

US State Department spokeswoman Victoria Nuland said Washington hoped for even broader sanctions.

"So these (EU measures) are the kinds of steps that we would like to see not just from our close allies and partners in places like Europe but from countries around the world," she said.

"Because we do believe that this is consistent with tightening the noose on Iran economically," she said. "We think that the place to get Iran's attention is with regard to its oil sector."

Amid the tension, Iran saw turmoil on its domestic currency market, with authorities trying to shore up the rial following its slide to a record low on Monday days after Washington enacted new sanctions targeting the central bank.

In a related development, the US Treasury said Secretary Timothy Geithner will travel to China and Japan next week to discuss tougher sanctions against Iran, after China said it opposed unilateral US measures.

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

Iran denies that allegation, saying the programme is entirely peaceful.

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