In the king's audience hall at the palace in Jeddah last year, a group of Saudi Arabian princes was waiting for the president of Sudan to arrive when a mobile telephone rang. It was September 11. 

The house of Saud was about to learn of the terrorist assaults that would plunge the secretive kingdom into a series of political and military crises that are now testing Riyadh's relations with the West. 

The first call announced that a plane had crashed into the World Trade Center in New York. 

"Nothing came into my mind about a terrorist attack," said Prince Turki al-Faisal, a former head of Saudi intelligence who was attending the royal reception. 

At lunch, news of the second assault arrived. "When the president of Sudan left the table, we immediately put the television on," the prince said. "There it was in full color. There was total amazement." 

"When the Americans started saying the same day that it was Al-Qaeda," said Prince Turki, "everyone here had this instinctive reaction: they are not capable of doing that." 

For the Saudi royals, glued to television sets like millions around the globe, there followed a bitter awakening to the harsh reality of Usama bin Laden's prowess. Not only was the mastermind of the world's worst terrorist atrocity the scion of a wealthy Saudi family, but 15 of the 19 suicide hijackers were Saudi citizens. 

Four months later the careful, polite, respectful ties that characterized Riyadh's political and economic relationship with America have dissolved in a whirlpool of suspicion and vitriol. A relationship based on mutual military self-interest and billions of dollars worth of oil is dangerously close to rupture. 

American complaints of Saudi perfidy have been countered by implied threats in Riyadh to expel U.S. forces from the country. Senior officials on both sides have ditched their habitual diplomatic reserve in favor of scathing criticism. 

Senator Joseph Lieberman, a leading Democrat, warned recently that Saudi Arabia risked isolation behind a "theological iron curtain." 

In Riyadh last week, Prince Nawaf bin Abdul Aziz, the crown prince's brother and Prince Turki's successor as head of intelligence, said: "The policies that America uses in the Middle East are not resulting in a peaceful settlement in the area. America is always with Israel. This is very bad." 

Despite efforts on both sides to defuse the crisis, some of Riyadh's most eminent citizens are publicly calling for American troops to leave the Saudi bases that have been a cornerstone of U.S. strategic planning in the region since the Gulf War against Iraq. 

"Since September 11, America has lost the Saudi people," said Dr Abdulrahman al-Zamil, chairman of the Al-Zamil business group and a member of the shura, the consultative council. 

"America tried to convince people that they are here to protect the regime, and this is total garbage," al-Zamil said. "Their presence is a liability to the Saudi government. This is the worst period of crisis I have seen." 

Dr. Abdulaziz Alsebail, professor of Arabic literature at King Saud University and deputy editor-in-chief of the daily Saudi Gazette, said many Saudis had long admired America. 

"Many of us and our children have been educated there and even born there," said Dr. Alsebail. "But after September 11, questions were raised. Should Saudi Arabia stay loyal to the United States? Nobody is happy that the American forces are here." 

In America there have been similar doubts. James Woolsey, a former CIA director, claimed that "much of the money for Al Qaeda has come from Saudi Arabia." 

Congressmen complained that Riyadh had never co-operated fully with the FBI's investigation into the 1996 bombing of the U.S. military barracks in Dhahran. 

Sen. Carl Levin, D-Mich., the influential chairman of the Senate Armed Services Committee, said U.S. forces needed a base in the Gulf region, "but it seems to me we should find a place that is more hospitable." 

The American media compared Saudi restrictions on women to those of the Taliban regime in Afghanistan, while Jewish groups denounced Riyadh as anti-Semitic. 

There was even a legal row over the Pentagon's rule that female military personnel stationed in Saudi Arabia should wear head-to-toe robes whenever they leave their base; the rule was scrapped after a lawsuit by the American air force's most senior female fighter pilot. 

Both Princes Turki and Nawaf last week denied persistent American reports that U.S. forces will soon be asked to leave. 

"The fundamentals of the Saudi-American relationship have not changed," Turki said. "The government decision stands." 

Nawaf emphasis ed, however, that tension will continue as long as Washington fails to curb Israeli attacks on Palestinians. Even before the terror attacks, Crown Prince Abdullah wrote to President George W. Bush warning that "a time comes when people and nations part." The prince said Washington and Riyadh should now "look at their separate interests." 

Nawaf complained that Washington obstructed all attempts to condemn Israel at the United Nations. 

James Akins, a former American ambassador to Riyadh, warned last week that the Bush administration's handling of Middle Eastern issues was jeopardizing a crucial relationship. 

"Oil is going to be an American interest for ever." he said. "There's every reason for us to be interested in stability in Saudi Arabia." The region has two-thirds of the world's proven oil reserves. 

Akins added: "The reason we are hated in Saudi Arabia is that we have a double standard. We allow Israel to get away with breaking international law and defying U.N. Security Council resolutions. As long as that condition maintains, the relationship with Saudi Arabia and other Muslim countries is going to be very bad." 

Other American experts warned that any breach between Riyadh and Washington would play into the hands of bin Laden, who has vilified the Saudi royal family for allowing 5,000 American troops to be based in the country that houses the Muslim world's most important religious shrine at Mecca. 

The spread of radical Islam in the region has compelled the Saudi royal family to enforce numerous restrictions on U.S. military activities in the country, and American warplanes stationed at the Prince Sultan air base near Riyadh have been barred from carrying out bombing raids on Iraq. 

"If we pull away from the Saudis, bin Laden will have won a major victory," warned Anthony Cordesman, a former Pentagon planner. Riyadh was responding to one of Washington's biggest complaints, he said, by making progress in cutting off terror group funds. 

"We need to fix our strategic relationship with Saudi Arabia, not break it," he said.