Iran has said it will act preemptively against its enemies if it feels its interests are threatened, according to national media.
In a thinly-veiled threat to Israel, the deputy head of Iran's armed forces said that it will not wait to be attacked before defending itself.
"Our strategy now is that if we feel our enemies want to endanger Iran's national interests, and want to decide to do that, we will act without waiting for their actions," Mohammad Hejazi told the Fars news agency.
The statement comes two days after the UK and United States both warned Israel against making any pre-emptive attack on Iran.
British foreign secretary William Hague insisted that Israel must give economic sanctions more time before taking military action.
Israel launched pre-emptive strikes against a reactor in Iraq in 1981, to the dismay and shock of the United States, and some inside the country have mooted similar attacks against Iranian facilities.
However the country has also come under domestic pressure to heed America's warnings about the dire implications of an attack on regional and world diplomacy.
In an editorial titled 'An American Warning', the Israeli Haaretz newspaper said that fear of Iran was pushing the government into a "dangerous corner".
The country "must listen to the warnings coming out of Washington and refrain, for now, from unilateral measures" the editorial said.
Meanwhile a United Nations delegation arrived in Iran on Monday for two days of talks in an attempt to ease international tension over its nuclear ambitions.
Iran insists its uranium enrichment programme is peaceful in nature, but many countries including the United States say there is evidence that iran is building atomic weapons.
A range of new sanctions have been imposed on Iran in an attempt to pressure them into halting its nuclear programme, but so far the regime has remained defiant.
The UN said its five-man negotiating team will attempt to scope the possibility for a peaceful solution.
"We hope to have a couple of good and constructive days in Tehran," said Herman Nackaerts, the deputy-director general of the UN International Atomic Energy Agency (IAEA), before departing for Iran from Vienna.
"The highest priority remains of course the possible military dimensions of Iran's nuclear programme."
Iran insists it is open to the talks, and will work towards a solution if one is possible.
"We are looking for a mechanism for a solution for the nuclear issue in a way that it is win-win for both sides," said Ali Akbar Salehi, the oil minister.
However diplomats have played down the chances of a serious breakthrough, and Iran has already confirmed the UN team will not be visiting any nuclear sites.
On Sunday Iran confirmed it would "cut" oil exports to companies in France and the UK, ahead of EU sanctions scheduled to come into force on 1 July.
"We will sell our oil to new customers," a ministry of oil spokesperson was quoted as saying.
Last week Iranian president Mahmoud Ahmadinejad attended a ceremony at which domestically-produced nuclear fuel was used in a reactor for the first time.
The Iranian regime also docked two ships in Syria on Monday, in an apparent show of support and solidarity for President Assad's regime and its struggle against the armed opposition to his rule.