Saudi Crown Prince Abdullah sent an extraordinary letter to George Bush. "... a time comes when peoples and nations part. We are at a crossroads," he wrote. "It is time for the United States and Saudi Arabia to look at their separate interests. Those governments that don't feel the pulse of the people and respond to it will suffer the fate of the Shah of Iran."
Palestine is the key issue on which there was serious divergence.
Since last spring Crown Prince Abdullah has been urging Mr Bush to launch a new drive to reach a final settlement between Palestinians and Israelis. Mr Bush has kept his distance. On Thursday, Saudi Foreign Minister Saud al-Faisal said the Bush administration's attitude "makes a sane man go mad."
Such frank talk from Washington's oldest and closest ally in the Middle East must be taken seriously because for 70 years the Saudi-US relationship has been one of the three main props of the House of Saud.
Since the September 11th attacks on the World Trade Centre and the Pentagon, the fabric of the connection has frayed to the point of parting.
The man accused of masterminding the operation, Osama bin Laden, and 15 of the 19 suspects believed to have been involved were Saudis motivated by the fundamentalist, anti-Western ideology promulgated by the puritanical Wahhabi sect, the second prop of the House of Saud.
While the official clerical establishment supports Riyadh's decision to endorse the US anti-terror campaign, dissident clerics claim, "Those who support the infidels [non-Muslims] and help them against Muslims are infidels."
Although the dissidents have not directly accused the House of Saud, they are clearly asking whether it has abandoned the compact made by its founder, Abdel Aziz ibn Saud, with the Wahhabi sect. This questioning undermines the regime's legitimacy with the Wahhabi constituency which comprises only about 20 per cent of the populace.
The third prop is oil. But oil revenues have not won the loyalty of the bulk of the kingdom's population. Development funds were spent mainly in the central Najd province, the Wahhabi heartland, and on infrastructure in the holy cities of Mecca and Medina. The provinces remain poor, backward and prone to influence by dissident preachers.
Fluctuating oil prices, heavy expenditure on defence, the export of investment capital and rampant corruption have halved Saudi per capita income over the past decade.
The government has been compelled to curtail funding of education, health and welfare programmes as unemployment rose to 30 per cent.
Mai Yamani, a Saudi-born fellow at the Royal Institute of International Affairs in London, says, "There are big frustrations building up in Saudi Arabia ... We have a radical dissent that is voiced in Islamic language." She warns: "At the moment, what is dangerous about the situation is that it is totally unpredictable."
It is significant Crown Prince Abdullah mentioned the ill-fated Shah of Iran in his letter to Mr Bush.
Over the past five years, there has been serious speculation over the durability of the House of Saud. The CIA, which conducted rigorous study on the kingdom, concluded it was not headed for an Iran-style Islamic revolution.
Since September 11th, agency analysts have become less certain. The parallels between the two countries are striking.
Saudi Arabia, like Iran under the Shah, is an authoritarian, free-spending monarchy dependent on US political and military support. The House of Saud is castigated from all sides: by Islamists for not being Islamic enough, by nationalists for relying on the US connection and by liberals for repressive policies and human-rights abuses.
The main difference is that the Shah was determined to transform Iran into a modern, secular state while the Saudis have attempted to marry ultra-conservative religious ideology and practice with 20th-century advantages. Both experiments failed.
The House of Saud is expected to survive as long as Crown Prince Abdullah is in charge. He is popular because he is seen as a devout, austere and incorruptible reformist. Since taking power in 1998 after King Fahd was incapacitated by illness, Prince Abdullah has attempted to curb the excesses of the 7,000 leading royals, adopted a pan-Arab foreign policy and taken a strong stand against Israel.
A former US ambassador to the kingdom, Mr. James Akins, believes the Saudi monarchy will survive. "You can't say that an absolute monarchy is the wave of the future, but I don't think a regressive religious dictatorship is the wave of the future either."
The slow-moving royals may not have the time to put in place the representative institutions needed to replace the crumbling props which have sustained the House of Saud for so long.