CIA director Michael Hayden on Saturday personally delivered a message from US President George W. Bush to Saudi Arabia's King Abdullah, the official SPA news agency said.
Although it did not elaborate on what was discussed, Hayden's visit came a day after Western naval forces in the Gulf were reportedly on heightened alert for possible sea-borne attacks against the world's largest oil-producing country.
Hayden met the king, Saudi intelligence head Prince Miqren bin Abdul Aziz and senior advisers to the monarch at the Red Sea Port of Jeddah, the agency said.
Oil installations in Saudi Arabia are a "high-probability potential target" for terrorist attack, but tight security measures are in place to protect them, interior ministry spokesman General Mansur al-Turki said on Friday.
"Coalition forces are taking prudent, precautionary measures and focusing maritime security operations in the Gulf on these possible threats," a Bahrain-based spokesman for the coalition naval forces told AFP.
Lieutenant Commander Charlie Brown said the measures were "in response to recent threats to oil infrastructure in the Gulf, including public statements by Al-Qaeda leadership".
In Washington, a senior state department official speaking on condition of anonymity confirmed the existence of a threat, but added: "I can't tell you the level of specificity or anything else."
On Thursday Saudi security forces arrested two suspects at Sajir, 300 kilometres (185 miles) west of the capital, the London-based Saudi daily Al-Hayat reported on Saturday, citing an interior ministry spokesman in Riyadh.
One of those held had just finished his studies at King Fahd University of Petroleum and Minerals at Dhahran on the coast of the Gulf in the oil-rich eastern province.
His elder brother was also held because "he is suspected of belonging to the deviant minority" -- the official Saudi term for Al-Qaeda militants who launched a wave of attacks in the kingdom three and a half years ago -- Al-Hayat quoted security sources as saying.
Saudi Arabia pumps more than nine million barrels of oil per day and sits on a quarter of global oil reserves. It operates the world's largest oil terminal at Ras Tannura on the Gulf.