Whether this is in the form of a full scale invasion with the intention of regime change, in which case it will probably be delayed until some degree of stability has been enforced on Iraq or it could take the form of a short sharp air campaign designed to destroy as much as possible of Iran's Nuclear, Missile and Command Control infrastructure.
This latter course, the neo-cons in Washington are apparently convincing themselves, would also seriously undermine the conservative anti-American element of Iran's present leadership.
Iran is well aware that despite years of effort put into attempts to both harden and hide vital sections of its scientific research and weapons programs, it still remains highly vulnerable to any high tech or sustained American air assault.
Nor is America the only nation seen as a threat by Tehran. Israel with its large and effective fleet of long range F15 and F16 strike aircraft equipped with sophisticated weaponry is capable of delivering a devastating blow to Iran's military capability.
Israel too has gained major new tactical advantages as its aircraft can now operate safely over a compliant Jordan and an occupied Iraq.
The Israeli air force is also to be the recipient of an enormous boost to its offensive capability with the delivery of some 5,000 US 'smart' air launched weapons including some 500 so-called 'bunker-busters' capable of penetrating reinforced concrete or deep underground facilities before exploding.
Given Israel's already substantial holdings of such weapons, this increase in its inventory would allow a sustained assault with or without further US involvement Israel is unlikely to miss out on the chance of destroying the only serious potential Islamic nuclear threat to its existence if and when Washington gives the appropriate signal.
Iran finds itself in the invidious situation that while it is a committed Islamic state, it does not see itself as an integral part of the Arab world.
Indeed Tehran is fully aware that many in the wider Arab world, not just the Gulf states, actively dislike Iran and have good historical reasons for fearing their militarily strong and assertive neighbour.
Iran therefore has few genuine allies and while many Arab nations will be uncomfortable with growing US influence in the region, they would at the same time rather enjoy seeing Iran's increasing military power severely reduced.
Iran on the other hand believes that as a major nation for many centuries it has the same rights of national defence as Britain, the United States, India or for that matter Israel.
This includes the possession of advanced strategic missiles systems and a nuclear weapons capability, and much of the leadership in Tehran bitterly resents what it sees as a Western bias that allows a gross and growing imbalance in the Middle East with Israel being allowed, if not encouraged to become a regional nuclear superpower.
Iran has been at the receiving end of continuing US interference in its political system for over half a century.
In 1953 a joint US-British intelligence operation to subvert the legally elected government of Premier Muhammad Mossadegh led to a successful coup and the restoration of a dictatorial pro-Western regime, while since the Islamic revolution of 1978-79 which finally removed the Shah, US attempts to either covertly influence or subvert the government of Iran have multiplied.
Tehran is fully aware that in recent months the CIA and exile Iranian groups have redoubled their clandestine operations within Iran to identify potential targets, to create civil unrest and to subvert the officer corps of the army and air force. US success in neutralising large numbers of senior Iraqi commanders has been noted with alarm in Iran and indeed the CIA has been in contact with senior Iranian military personnel for several years and is believed to have developed a number of highly valuable operations to undermine Iran's defences.
However, and crucially, they are believed to have so far failed in similar attempts with the Islamic Republican Guards or Pasdaran.
The defensive course that the Iranian government has apparently decided on is to ensure a higher degree of integration between the Pasdaran and regular army formations in potential conflict situations and to increase both the penetration of the army by the internal security branch of the intelligence service, SAVAMA, and vastly increase the numbers of trusted Pasdaran officers positioned at brigade and divisional-level headquarters to watch for any signs of treachery by regular officers, much in the manner of commissars or political officers that the Soviets used to deploy.
In a parallel move the Iranian government is believed to have already moved hundreds, if not thousands, of trusted Islamic officers and Pasdaran fighters into the Shi'ite areas of Iraq in order to be able to create a massive subversive campaign behind US lines in the event of an attack on their country.
Iran has also made considerable efforts to ensure the survival of its political and military leadership in the event of war.
Though regularly denied in Washington, it would appear that specialist task forces formed with CIA paramilitaries and members of the Delta Force, as well as the little known 'Gray Fox' units of the US army's highly secretive intelligence support activity or ISA have operated as dedicated assassination squads in both Afghanistan and Iraq.
The determination to kill significant numbers of the leadership and paralyze the chain of command at the outset of a conflict by smart bombs, Cruise missiles, explosive devices or bullets is now a well established US strategy. The Iranian leadership will undoubtedly be heavily targeted in the same manner in the event of war.
SAVAMA are now believed by some observers to have a dedicated program in place to both protect the nations command structure and significantly, also to be in a position to threaten some form of retaliation against Western leaders.
It is self-evident that Iran does not see itself as a pariah state or in serious breach of any international agreement, and while still vehemently protesting its position, Tehran has shown itself prepared to make what on paper at least, appear to be concessions to avoid conflict. It was reported on November 14 that Iran had notified the UN nuclear watchdog that it is prepared to suspend uranium enrichment and linked activities in order to dispel American suspicions that it is actively seeking to build nuclear arms.
Whether this is a genuine step away from confrontation or just a response to the re-election of George W Bush is unclear.
However the resignation of Secretary of State Colin Powell and his replacement by Condoleezza Rice, the president's present national security adviser, will inevitably see the removal of a major moderating influence on foreign policy and possibly change the balance of power in Washington in favour of a more aggressive and assertive US policy towards not only Iran, but North Korea, China and Russia as well.
From Tehran's viewpoint its status in Washington now appears to be that of a domino waiting to fall.
As Iran's leadership looks outwards it both sees and fears the ever tightening ring of US military bases being created around it in the Gulf, Pakistan, Afghanistan, the former Soviet Central Asian states, Turkey and now Iraq.
The latter in particular is strategically highly significant with its long and highly vulnerable land border. Iraq is the natural jumping off point for any future invasion force and a prolonged insurgency tying down large numbers of US troops must be in Tehran's interests.
However short of a significant climb down by Iran on both Weapons of Mass Destruction and its overt support for Hezbollah and what Washington considers to be Islamic terrorist groups or a major and unlikely reversal of US foreign policy, then some form of conflict now seems inevitable.
Iran's recent testing of the long range Shehab-3 missile system gives it the basis of a reliable and accurate strategic capability.
Neither America nor Israel will be tempted to delay action until such systems become fully operational.
Iran is therefore likely to be faced with very tough decisions within the next few months, and those decisions could well change the face of the Middle East forever.