TEHRAN (AFP) - Three years after the launch of the US-led war that ousted Iraqi dictator Saddam Hussein, the Shiite clerical regime in neighbouring Iran is now clearly in Washington's sights over its nuclear ambitions.
But barely had the White House declared Iran its number one threat, than Tehran said it was willing to talk to its arch-enemy over Iraq, currently teetering on the brink of all-out civil war.
Washington, which once branded Iran as part of an "axis of evil" with North Korea and Saddam's Iraq, has been piling the pressure on Tehran over its nuclear programme and accusing it of meddling in Iraq.
The White House this week bluntly warned both Iran and North Korea that it would take preemptive military action if necessary to protect itself, making no apologies for the war in Iraq.
"We may face no greater challenge from a single country than from Iran," the White House said in a blueprint called the "National Security Strategy" obtained by AFP on Thursday.
Washington has been spearheading the international campaign against Iran over its nuclear power efforts, which the United States claims is a cover for efforts to develop atomic weapons -- charges vehemently denied by Tehran.
President George W. Bush had made Saddam's alleged possession of chemical and biological weapons and pursuit of nuclear arms the centrepiece of his case for war, but no such weapons have been found.
"There will always be some uncertainty" about banned weapons programmes, the White House said. "We have no doubt that the world is better of if tyrants know that they pursue WMD at their own peril."
The Shiite regime in Iran is also under attack from Washington for allegedly seeking to sow instability in Iraq by helping arm Shiite militias amid spiralling inter-communal violence.
Iran's new hardline President Mohammed Ahmadinejad has only added fuel to the fire with his fierce anti-Western rhetoric and his defence of the country's nuclear programme.
Ironically, the US-led invasion gave a massive boost to Iran as a regional power and to Shiite communities across the Middle East, a region traditionally dominated by Sunni Muslims.
Iran, which has a population of 69 million and is OPEC's number-two oil exporter, also enjoys a strategically important geographical position, with links to the Arab world to the west, Asia to the east and Russia to the north.
But the presence of US forces in Iraq is regarded in Iran as a potential danger. That is added to Tehran's oft-spoken concerns about its other arch-enemy, Israel, widely believed to be the only nuclear-armed power in the Middle East with an arsenal of at least 200 warheads.
Ten days after US troops invaded Iraq on March 20, 2003, Tehran warned that it would not support any administration installed by the Americans but said it would give a favourable welcome to a government formed after a popular vote.
Three years on, Iran has probably got the political result it wants with its Shiite allies now in power in Baghdad after decades of Sunni-led oppression under Saddam.
Tehran has enjoyed longstanding close ties with what is now the ruling Shiite alliance in Iraq, many of whose leaders were exiled in Iran during Saddam's iron-fisted rule.
Leaders of the Shiite party Dawa of Iraq's outgoing prime minister Ibrahim Jafaari took refuge in Iran during the 1980s, when Saddam's regime was at war with Iran.
The main Shiite movement, the Supreme Council for the Islamic Revolution in Iraq, headed by Abdul Aziz al-Hakim, was itself created in Tehran in 1982. SCIRI's militia, the Badr Corps, was trained by the Iranian military and Iraq's ousted Sunni elite regularly accuses the group of killing army veterans and old regime supporters in collaboration with Tehran.
Perhaps more worrying for the Americans is the powerful role in Iraq played by firebrand Shiite leader Moqtada Sadr, who vowed during a visit to Iran in January that his Mehdi Army militia would support any of Iraq's Muslim neighbours if they were attacked.
Tehran said Thursday it was ready to negotiate with the United States, derided in Iran as the "Great Satan," to help stabilise Iraq. Such talks would be the first direct talks since Washington broke ties with Tehran in April 1980 after the Islamic revolution and the seizure of US hostages.
The White House said any such talks would have a "very narrow mandate" and would not cover the nuclear crisis or any other disputes.
And with the UN Security Council still locked in talks on how to tackle the nuclear crisis, US Secretary of State Condoleezza Rice made clear Thursday there would be no let up against Iran, calling it the "central banker of terrorism".