IRAN'S historic ambitions to be the dominant regional power mean it will not be dissuaded from its long-term goal of nuclear weapons, creating the prospect of an eventual showdown with the US and its allies.
That is the view of US Deputy Secretary of State Richard Armitage, who also says the Iranian ambition to be the world centre for Shia Muslims is driving its "dangerous game" in neighbouring Iraq.
Mr Armitage made the comments on US television in a pessimistic assessment of the prospects for Iran, which has agreed with European nations to suspend the nuclear enrichment program it insists is for power generation only.
"I don't believe in the long run the Iranians will be dissuaded from this program and we're going to have to consider all our options with our friends and allies," he said.
In an insight into the Bush administration's thinking on one of the most potentially difficult foreign policy problems the US will face in the next four years, Mr Armitage argued that a historical perspective was vital to understanding the Iranian psyche.
Mr Armitage has resigned as the State Department No2, but will remain until early next year.
He said he had served as an adviser to the Shah of Iran's special forces soldiers before the revolution in 1978-79.
"I believe that Iranians, who are perfectly congenial and wonderful one-on-one, in a group are quite ethnocentric, nationalistic and indeed hegemonistic," he said. "They think they're still at the time of Xerxes and Persepolis (a reference to the Persian king from 485BC to 465BC and his capital).
"I think it's not for nothing they call it the Persian Gulf and not the Arabian Gulf.
"So I think that they have, in the minds of the Iranian leadership, a great desire to be a much bigger player in the region."
The political reform movement in Iran gave little hope of a different outlook, he said. "I think the reform movement is misnamed. I think there are some who wanted a little more breathing room in their own life, but if you assume the reform movement is one that would eschew nuclear weapons and does not hold the same dreams of glory for Iran, I think you'd be wrong."
Asked if the use of force was the last resort with Iran, Mr Armitage said it would be irresponsible to discuss that publicly, but said the standard US statement was that "all options are on the table".
Iran should take notice of Libya's Muammar Gaddafi, who had given up his ambitions for weapons of mass destruction, saying it had brought him more headaches than benefits, he said.
Iran's ambition to be the world centre of the Shia Muslim religion was largely behind its efforts to influence Iraq's politics, he said.
"In terms of Iraq, they're playing a very dangerous game. They're using money, primarily, and in some cases, weapons, to try to subvert the south, the southern part - the Shia part of Iraq.
"They're trying to buy influence. I think ultimately they will fail in this, but they're playing a very dangerous game. I think Iran wants to have an Iraq that certainly is no threat to them, but moreover, aids them in their ability to become the, sort of the - what would you say? - world centre for Shia."