US sources yesterday confirmed reports that Saudi Arabia may be considering buying nuclear weapons from Pakistan or elsewhere in a move which could spark a new arms race in the volatile region.

The intelligence comes less than a month after the last American soldier left the desert kingdom to defend itself in the face of growing internal Islamic unrest and the prospect of neighbouring Iran developing atomic firepower.

A report in The Guardian quoted a leaked strategic document from Riyadh, the Saudi capital, outlining three options facing the beleaguered regime.

The document, said to be under consideration at the highest levels of the feudal Saudi government, says the kingdom would have to buy nuclear warheads, enter into a protective treaty with an existing nuclear power, or push on the international diplomatic front for a nuclear-free Middle East.

The US pulled out its forces and withdrew the umbrella of American military might in August after 13 years of maintaining troops and aircraft at bases within striking distance of Iraq.

The move, part of a US global redeployment, was also seen as retaliation for the Saudi refusal to allow its territory to be used for the invasion which toppled Saddam Hussein and reluctance to tackle terrorist funding by its own religious militants.

Washington has also never quite forgotten the fact that 15 of the 19 September 11 al Qaeda suicide hijackers were Saudis.

A US intelligence source said: ''The Saudis opened a secret nuclear research facility at the remote Al-Suleiyel military complex in thedesert in 1975. Their scientists co-operated with Saddam's on a weapons programme, but it never amounted to much. Not enough expertise and no nuclear power plants for the raw materials.

''Although they denied it at the time, their next attempt to join the nuclear club came just after Pakistan developed nuclear weapons in the late 1990s. There was a secret royal visit to the Kahuta uranium enrichment plant and the nearby factory where Islamabad's Ghauri missile is made.

''That site was so secret that even the Pakistani prime minister, Benazir Bhutto, was not allowed to go there during her tenure in office. Saudi money talked.''

The Saudis already have up to 60 Chinese-made CSS-2 ballistic missiles capable of delivering nuclear warheads.