Today's encounter between the veteran Saudi Foreign Minister, Prince Saudi al-Faisal, and the US Secretary of State, Mr Colin Powell, could decide the extent to which Riyadh co-operates with Washington in its anti-terror campaign. Sharing information is particularly urgent because 14 of the 19 suspects in last week's devastating attack are said to be Saudi nationals.
While the activities of the man Washington accuses of being the terrorist mastermind, Osama bin Laden, have created deep pain and embarassment in Saudi Arabia, Riyadh will find it difficult to balance its own national interests with US demands.
Bin Laden remains an admired as well as a reviled figure on the Saudi scene.
He was born into a Saudi-based Yemeni family which made its fortune constructing palaces for the royal family. In 1964 bin Laden's father convinced the ailing King Saud to relinquish the throne in favour of his half brother, Prince Faisal, father of the Foreign Minister.
In 1979 bin Laden put himself, his $250 million fortune and the family firm at the service of the Saudi-US cause of ousting the Soviet Union from Afghanistan.
He fell out with the ruling family after Baghdad invaded Kuwait in 1990.
He insisted that Saudi Arabia opt for self-defence rather than for US protection to deter an Iraqi attack on the kingdom.
Many Saudis agreed with his stance at the time.
The continuing presence of US forces on sacred Saudi soil remains a source of friction between the two countries.
Bin Laden was deprived of his citizenship in 1994 after his disciples were accused of murdering 18 US soldiers during the pacification campaign in Somalia and of participating in the first attack on the World Trade Centre.
Since then bin Laden's name has been associated with bombings at US military installations in Saudi Arabia in 1995 and 1996 and embassies in East Africa in 1998 as well as last week's outrages in the continental US.
The Middle Eastern country with the most to lose if it joins the US "crusade" against terrorism is Saudi Arabia.
The secretive and suspicious Saudis may be compelled to compromise their sovereignty by permitting US law enforcement agencies to have full access to militants and material on anti-US groups inside the kingdom.
While the Saudis have shared evidence gathered on those accused in the 1995 and 1996 bombings, they have not co-operated to the extent demanded by Washington and none of the suspects has been extradicted to the US for trial.
Washington may ask Saudi Arabia to permit its military bases to be used as staging areas for attacks on Afghanistan, bin Laden's refuge.
This would be seen by many ordinary Saudis as capitulation to a US diktat. Relations between US and local troops at Saudi bases have become increasingly strained over the past six months because of the Bush administration's refusal to assume an active role in Arab-Israel peacemaking.
As a sign of their disapproval, the Saudis have banned US importation of certain types of weaponry.
Washington has also been obliged to issue security warnings to its civilians living and working in the country because of widespread anti-US feeling.
While bin Laden is now regarded by Riyadh as a liability, Saudi Arabia enjoys a close political and economic relationship with the Taliban, which controls 90 per cent of Afghanistan.
Only Saudi Arabia, Pakistan and the United Arab Emirates recognise the Taliban as the legitimate Afghan government. While the creation of the Taliban was a joint effort by Pakistani Islamic scholars and military intelligence, the source of Taliban inspiration and practice is the ultra-conservative Saudi Wahhabi movement.
Wahhabi tribesmen swept Abdel Aziz ibn Saud, the founder of the ruling dynasty, into power in the 1920s. Indeed, the Taliban is a step-son of Wahhabi Arabia.
The movement enjoys considerable support among clerics and wealthy citizens who financed its rise to power and have major investments in Afghanistan.
The Taliban is still regarded by Riyadh as the main Sunni (Orthodox) asset in the struggle for control of strategic Afghanistan waged by Sunni Pakistan and Shia (heterodox) Iran.
Therefore, Saudi strategists are likely to see co-operation with a US assault on the Taliban as prejudicial to their country's own security.
