US Defense Secretary Leon Panetta on Thursday warned of the risks from any military strike on Iran, saying it could have a "serious impact" on the region without halting Tehran's nuclear program.

"You've got to be careful of unintended consequences here," he told reporters.

"Those consequences could involve not only not really deterring Iran from what they want to do, but more importantly it could have a serious impact on the region and it could have a serious impact on US forces in the region."

The Pentagon chief said he agreed with the view of his predecessor, former defense secretary Robert Gates, that bombing Iran would only delay the nuclear project by about three years.

Panetta said the United States was focused on diplomacy and was holding talks with allies to impose "additional sanctions" on Iran over its nuclear work. A strike on Iran ought to be "a last resort," he said.

Panetta's comments coincided with rising tensions with Iran after a UN report cited proof that Tehran's atomic program was being used to develop nuclear warheads.

Israel has signaled it may stage air strikes against Iran's nuclear sites while Tehran on Thursday threatened to hit back against any attack or even the threat of military action.

Asked if the United States could tolerate a nuclear-armed Iran if sanctions fail, Panetta said he hoped it would not come to that.

He said that "it is important that the world come together to apply sanctions against Iran and make very clear to them that they are going to pay a heavy price if they continue along this track.

"As to what happens down the road, you know, I think our hope is that we don't reach that point and that Iran decides that it should join the international family."

Iran's supreme leader, Ayatollah Ali Khamenei, meanwhile said the country "will respond with full force to any aggression or even threats in a way that will demolish the aggressors from within."

He said the message was directed at Iran's enemies, "especially America and its stooges and the Zionist regime (Israel)."

The supreme leader's forceful language followed threats last week from Israel that air strikes could be in the offing against Iran's nuclear facilities.

Israeli President Shimon Peres said on Saturday such action was becoming "more and more likely."

Iran warns of 'full force' response to threats
Tehran (AFP) Nov 10, 2011 - Iran will hit back against any attack or even threat of military action, the country's supreme leader said Thursday after Israel warned the world must act to prevent Tehran getting nuclear weapons.

Iran "will respond with full force to any aggression or even threats in a way that will demolish the aggressors from within," Ayatollah Ali Khamenei told students at a Tehran military college, according to his official website.

Khamenei said the message was directed at Iran's enemies, "especially America and its stooges and the Zionist regime (Israel)."

The supreme leader's forceful language followed threats last week from Israel that air strikes could be in the offing against Iran's nuclear facilities.

President Shimon Peres said on Saturday that such action was becoming "more and more likely."

But US Defence Secretary Leon Panetta Thursday warned of the risks of a military strike on Iran, saying it could have a "serious impact" on the region without halting Tehran's nuclear programme.

"You've got to be careful of unintended consequences here," Panetta told reporters in Washington.

"And those consequences could involve not only not really deterring Iran from what they want to do, but more importantly it could have a serious impact on the region and it could have a serious impact on US forces in the region."

Rhetoric between Iran and its two principal foes, Israel and the United States, has risen since the release on Tuesday of a UN report saying there was "credible" evidence suggesting Iran's atomic programme was being used to research putting nuclear warheads in ballistic missiles.

Iran, which has long denied any military thrust to its nuclear programme, responded to the report saying it would not budge "an iota" from its atomic course and asserted it could confront any attack.

Defence Minister Ahmad Vahid was quoted by state media as saying "the armed forces of the Islamic republic will powerfully respond to any aggression and threat... Any (action) by the usurper regime (of Israel) will spell its demise."

A day earlier, armed forces deputy chief Brigadier General Masoud Jazayeri also predicted Israel's "destruction" if it attacks and warned: "Our response would not be limited to the Middle East."

"Iran is not a nation to sit still and just observe threats from fragile materialist powers which are being eaten by worms from inside," Khamenei was quoted as telling the military cadets on Thursday.

"Anyone who harbours any thought of invading the Islamic Republic of Iran -- or even if the thought crosses their mind -- should be prepared to receive strong blows and the steel fists of the military, the (Revolutionary) Guards, and the Basij (militia), or in other words the Iranian nation," he said.

Israeli Prime Minister Benjamin Netanyahu said on Wednesday "the international community must bring about the cessation of Iran's pursuit of nuclear weapons which endanger the peace of the world and of the Middle East."

Although he did not say what action Israel was looking at taking, media reports last week said he and Defence Minister Ehud Barak were seeking cabinet support for a pre-emptive Israeli attack on Iran.

Israel last week carried out what national media called a "ballistic missile" test, as well as a large-scale civil defence drill simulating the response to conventional and non-conventional missile attacks.

UN leader Ban Ki-moon also voiced his "serious concern" Thursday about the military dimensions to Iran's nuclear drive, saying it was up to the Tehran government to prove its peaceful intentions.

But the UN secretary general still "reiterates his belief that a negotiated rather than a military solution is the only way to resolve this issue," his spokesman Martin Nesirky told reporters.

Following the UN report, the European Union was preparing a new round of sanctions against Iran ahead of a meeting of its foreign ministers on Monday, diplomats in Brussels said on condition of anonymity.

Russia, which built Iran's first nuclear plant at Bushehr, has already ruled out support for any more sanctions against the Islamic republic before the UN Security Council, where it holds the power of veto.

The United States has said it is consulting with allies on ways to put "additional pressure" on Iran.

State Department spokesman Mark Toner said "a range of options" were being considered. "I don't want to rule anything out or anything in," he said.

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