Senator Richard Lugar says the Saudi government is providing the money to run Islamic schools, called madrassas, that teach their students dangerous lessons. "And out of these schools come young Saudis who join these militant organizations and who have very little regard for the American-Saudi relationship," he said.

Speaking on the Fox News Sunday television program, the Indiana Republican said this is a serious problem for the Saudis. He said, if attacks on foreign workers continue, the effect on the Saudi oil industry could be very severe.

"Six-million expatriates, essentially, run that industry," he said. "This is an oil industry that is based upon foreign workers, from executives down to the most menial tasks."

The Saudis insist they are doing everything possible to ensure the safety of foreign workers. But the spokesman for the Saudi Embassy in Washington, Nail Al-Jubeir, told CNN's Late Edition that protecting housing complexes from an attack by a small group of armed men is difficult.

"The question that we have is how do you protect against a lone gunman or four gunmen moving into an area, wanting to die, committing murder? It is very difficult to protect against," said Mr. Al-Jubeir. "You can protect against car bombs, you can put barriers against car bombs, you can protect as people try to come in, but it is difficult to guard individual buildings in a way that you are absolutely sure nothing is going to happen."

The Saudi spokesman went on to stress that, despite this weekend's attack on a foreign housing complex in the oil city of Khobar, the oil fields to the north are heavily guarded and safe.

He was asked what impact the terrorist siege in Khobar might have on the oil industry, and on Saudi Arabia's pledge last week to raise production in order to help bring down soaring world oil market prices. "Our attempt to increase oil production to help reduce the price of oil is going to have a little of a bump here in the next few days," he said. "Our speculators are waiting to see what is going to happen. Once they realize our oil installations are safe, and they are protected, we should see a down spill [reduction] in the price of oil."