The relationship with the Saudis has been a cornerstone of the US's strategic approach to the Gulf region. But could it be unravelling, asks Patrick Smyth.
Guardian at one time of both the West's lifeblood - oil - and Islam's holiest shrines of Mecca and Medina, the desert kingdom of Saudi Arabia straddles two civilisations and two ways of thinking.
And never more uncomfortably.
The US relationship with the Saudis has been a cornerstone of its strategic approach to the entire Gulf region. But is it in danger of unravelling? Recent media reports of unease in the kingdom, and, in Washington, the perception of a half-heartedness in Riyadh on the war against al-Qaeda, have prompted calls for a rethink in the US's approach to its old ally.
The Washington Post last week quoted senior anonymous Saudi officials close to Crown Prince Abdullah, the country's de facto ruler since King Fahd was incapacitated by a stroke in 1995, as saying the 5,000-strong US force based in the kingdom had "overstayed its welcome" and that other forms of less conspicuous military co-operation should be devised once the US has completed its war in Afghanistan.
Such a decision would deprive the US of regular use of the Prince Sultan Air Base, from which American power has been projected into the Gulf region and beyond for more than a decade.
The American presence has become a political liability in domestic politics and in the Arab world, Saudi officials are quoted as saying. And the Saudi government has become increasingly uncomfortable with a role in US efforts to contain Saddam Hussein, and earlier ruled out the use of Saudi territory as a base for bombing raids on Iraq.
Strategically, moreover, Riyadh sees itself as less dependent on the US for its own security. It has had a significant rapprochment with the once-feared Iranians, and Saddam is seen as less of a threat these days.
Prince Abdullah is also deeply personally perturbed by the failure of the US to curb the Israelis over Palestine.
In Washington there was a quick flurry of denials led by the Secretary of State, Colin Powell, who said he has had "no discussion" with Saudi officials about the possibility of the kingdom asking the US to leave.
And a former senior US Middle East diplomat dismissed the likelihood of such a call, arguing that Prince Abdullah, a popular and honest ruler with strong Arab nationalist sympathies, is much more secure internally than some recent commentaries suggest. He is also keen to maintain a good relationship with the US. There is still a lot at stake.
But in Congress the idea of a pull-out is finding friends. Some have seen September 11th as a wake-up call to the real nature of the Saudi regime as a seed-bed for terrorism and sponsor of fundamentalist Islam in its particularly intolerant Wahabist form.
Why were so many of the September 11th bombers Saudis, they ask. Why are the Saudis so slow to give details of other suspected terrorists? US News and World Report quotes US intelligence sources claiming that two Saudi princes have even paid protection money on behalf of the Saudi state to Osama bin Laden following the 1995 bombing of the Riyadh National Guard HQ which killed seven US military advisers.
The media has widely reported the funding of his teaching through the madrassah schools which the kingdom has opened throughout the Muslim world. And the US has complained that Saudi-base charities have been fronts for al-Qaeda fund-raising.
Senator Carl Levin, the Democratic chairman of the Armed Services Committee, said last week the US should consider moving its forces out. "We need a base in that region, but it seems to me we should find a place that is more hospitable ... I don't think they want us to stay there.
"The Saudis actually think somehow they are doing us a favour by having us be there helping to defend them," he said.
And in the journal Foreign Affairs, a former Assistant Secretary of State and Ambassador to Israel, Martin Indyk, has argued that the US should reverse its policy - partly his own - of turning a blind eye to Riyadh's brutally oppressive methods and failure to reform economically.
The Saudi-US relationship above all is about oil and money. In its present form it goes back to a 1945 meeting between President Roosevelt and King Abd al-Aziz Ibn Saud on a US warship on the Suez Canal, following the Yalta conference. Although still clouded in secrecy, the former is said to have promised the latter US protection in return for privileged US access to the county's oil from which it derives about one sixth of its crude oil imports.
President Jimmy Carter would later enshrine the policy in the "Carter doctrine", the rationale for the Gulf War: any attempt by a hostile power to seize control of the Persian Gulf would be regarded as an assault on the vital interests of the USA and would be resisted "by any means necessary, including military force".
Saudi companies buy some $6-10 billion in US goods every year. Over the past decade that has meant $33 billion in military hardware, more than Israel and Egypt combined - a bonanza for US industry.
Paid for by oil, the trade and the contracts that underpin it are also the source of the huge "commissions" - in reality bribes - that replaced the royal stipends, and are now the staple of the royal family's many princes' luxurious lifestyles. Saudi Arabia is little more than a blue-blooded kleptocracy, whose corruption has been viewed benignly by the US as the least worst alternative to democratisation and the possibility of Islamic fundamentalist control of the oil.
Prince Abdullah and his half-brother, the Defence Minister, Prince Sultan, represent the two antagonistic sides of Saudi's unresolved contradiction. The Royal dynasty's political future depends on Prince Abdullah's genuine attempts to reform the commission system, control the country's unhealthy penchant for deficit budgeting, and his ability to reach out to his 17 million people, voicing if necessary their anti-Americanism.
But its economic wellbeing, Prince Sultan believes, is intimately linked to US crony capitalism. He has criticised his brother's "confrontational" approach to the US.
US intelligence intercepts suggest a bitter power struggle between the two men, according to the journalist Seymour Hersh. He claims that King Fahd, a sick old man who rarely recognises friends, is being kept alive merely to prevent Prince Abdullah from becoming king.
And yet, by more than one account, were the king to die and the hated Prince Sultan to accede, the very demons of internal rebellion which western strategists fear could be unleashed.
And so, although frustrated by Saudi ambiguities over bin Laden and bin Ladenism, the Bush administration is playing this one sotto voce. And, certainly, stepping away is not in the game plan.
• Patrick Smyth is Washington Correspondent of The Irish Times.