Officials in Saudi Arabia say King Fahd is in stable condition, a day after being hospitalized for medical tests.
The royal palace has not said what is ailing the elderly monarch, but officials say he is suffering from a lung infection, possibly pneumonia.
News of the illness of the leader of the world's largest oil exporter, pushed world oil prices close to $52 a barrel Friday.
In Riyadh Saturday, a previously scheduled Gulf Cooperation Council summit went ahead as planned.
The king's half brother, Crown Prince Abdullah, will represent the kingdom at the summit. The Crown Prince has taken on many of the monarch's daily duties and acted as Saudi Arabia's de facto ruler since the king suffered a stroke a decade ago.