A Saudi Arabian officials says his country has rejected a US request to use its air bases for an offensive against terrorism, apparently due to concern about possible strikes on a fellow Arab state.
President George W Bush's administration blames a pan-Arab network of Islamic militants led by exiled Saudi dissident Osama bin Laden for the attacks on New York and Washington on September 11th that left more than 6,000 people missing or dead.
Officials indicate that a strike on Afghanistan, where bin Laden is in hiding, could come at any time.
But Saudi officials say the US can not use the Prince Sultan Air Base, south of the capital Riyadh, for retaliatory attacks.
Last week, the commander of the US Central Command's air operations, Air Force Lieutenant General Charles Wald, shifted his operations to the base from South Carolina.
The unnamed Saudi official says: "Saudi Arabia will not accept any infringement on its national sovereignty, but it fully backs action aimed at eradicating terrorism and its causes."
A spokesman for the US State Department says: "Saudi military co-operation with our international effort has been excellent."
He adds that Mr Bush and Secretary of State Colin Powell have said "there will be many facets to our international effort to bring to justice those responsible for the September 11 attacks, including efforts in law enforcement, diplomacy and international finance.
"As we move forward, we will be looking to the Saudis and others for assistance in these efforts."
The United States and Saudi Arabia have been close allies for more than 50 years. US troops have remained in the kingdom since leading the multi-national coalition which ended Iraq's invasion of Kuwait in 1991.