RIYADH -- American FBI and CIA agents joined the hunt for masterminds behind the suicide bombings in Riyadh, which U.S. Ambassador Robert Jordan compared to a Pearl Harbor or September 11 terror attack for Saudi Arabia.

Jordan also called the attacks on three expatriate housing compounds in which 34 people died as clearly an assault on Saudi Arabia's royal family. He said he was confident the kingdom's rulers were taking this seriously.

A team of up to 60 members of the Federal Bureau of Investigation and the Central Intelligence Agency arrived in the kingdom on Thursday to help the Saudi authorities hunt down those behind Monday's bombings in the world's biggest oil exporter.

The U.S. State Department warned Americans in Saudi Arabia of a report of a possible imminent attack targeted at the Red Sea port city of Jeddah.

"The U.S. Consulate General in Jeddah has received an unconfirmed report that a possible terrorist attack in the Al Hamra district of Jeddah may occur in the near future," the State Department said in a statement.

Jordan, who had criticized the kingdom for not responding quickly to U.S. warnings before the bombings, told foreign journalists on Thursday the attacks marked a watershed for Saudi Arabia's role in the global battle against terror.

"This was, if not the Saudis' September 11, certainly their Pearl Harbor," Jordan said, referring to Japan's attack on U.S. warships which brought the United States into World War II.

"There is a very clear suggestion that this ... was aimed at undermining the government ... as much as it was an attack on American interests ... to create fault lines," he said. At least seven Americans died in the attacks.

Jordan also said in a report on the British broadcasting Corp that the royal family "view this as their 9/11" -- the devastating attacks on the United States on September 11, 2001, blamed on the Al-Qaeda network.

"It's clearly an assault on the royal family and a fight to the finish with the royal family here in Saudi Arabia," Jordan said. --- Security Errors ---

Saudi Arabia admitted to security errors as U.S. Attorney General John Ashcroft said the bombings made clear Saudi Arabia had a "terrorism problem" that it must address.

Jordan had earlier criticized Saudi Arabia for not responding swiftly enough to U.S. demands for tighter security at residential complexes.

He urged U.S. dependants to leave the kingdom, telling American residents: "(Saudi Arabia) is a front in the war against terrorism. Women and children don't belong on the battlefield".

Some 40,000 Americans live in Saudi Arabia.

Interior Minister Prince Nayef told Reuters Saudi Arabia would cooperate with the FBI but rejected charges that militancy was a home-grown phenomenon.

"Where do the terrorists spring from? Other countries. Where do the smugglers come from? Other countries that should dry up these sources," he said, pointing to smuggling across the country's long desert borders and extremism on the internet.

Saudi officials, quoted in the local press, suggested the attackers received their orders directly from Saudi-born Al- Qaeda head Osama bin Laden, but a Saudi security source said such assertions were premature.

"We don't rule it out, but it's too early in the investigation to say this. There is no evidence so far," the source said.

Foreign Minister Prince Saud al-Faisal vowed to find those behind the bombings and said Al-Qaeda would regret its action.

The kingdom's ties with Washington have come under strain since the September 11 attacks, in which 15 of the 19 suicide airline hijackers were Saudis.

The U.S. State Department said eight Americans were killed in Monday's bombings and 17 were in hospital, one in critical condition. Official Saudi figures said seven Americans died.