Military doctors quickly performed a battery of tests on the 54-year-old president who is known for his hyperactivity. The Elysee palace said Sarkozy's test results were normal but that doctors would keep him under cardiological observation until Monday.
His office denied that Sarkozy had lost consciousness in the episode. The Elysee Palace statement followed reports from members of Sarkozy's government and his chief of staff who had indicated that Sarkozy had lost consciousness.
"Today, late in the morning, while he was jogging in the park at the Chateau of Versailles, the president of the republic felt unwell. This episode, which came after 45 minutes of intense physical activity, was not accompanied by a loss of consciousness," the palace statement said.
Sarkozy, an avid jogger and cyclist, was forced to interrupt his run and "lie down with the help of an aide," the statement said. A presidential doctor who is with Sarkozy at all times sounded the alert and administered initial treatment.
Doctors at the Val de Grace military hospital conducted neurological, blood and cardiological tests as well as an EEG, an electroencephalogram. Sarkozy, ever mindful of his image, received close advisers Sunday to keep up on the news and was resting, the statement said.
French Health Ministry Roselyne Bachelot said Sarkozy had suffered a "small" vasovagal episode.
A vagal episode can be caused by strenuous exercise when it is very hot. It can lead to a temporary loss of consciousness but usually is not serious. It is named for the vagus nerve which slows down the heartbeat and reduces arterial tension.
The Le Parisien newspaper on its Web site quoted Claude Gueant, the secretary-general of the Elysee Palace, as saying that Sarkozy's illness was over quickly.
"The president is completely conscious. His illness did not last a long time," Gueant said in the newspaper interview. Gueant, who was not with the French leader at the time, indicated that Sarkozy had been inanimate but he "had regained consciousness."
Gueant said Sarkozy had been jogging with his bodyguards on the grounds of the Lanterne pavilion, a hunting lodge at the Chateau of Versailles used by French presidents. Temperatures reached 28 degrees Celsius (84 degrees Fahrenheit) at Versailles on Sunday afternoon.
Earlier, the Elysee Palace had issued a brief statement saying that Sarkozy "felt faint" Sunday while exercising.
Sarkozy, 54, was elected in 2007. He last underwent a medical examination July 3, when his cardiovascular and blood tests were normal, the Elysee's medical service said.
His first medical bulletin issued shortly after his 2007 election said Sarkozy's health was "good" and compatible with his presidential duties. Since his election, Sarkozy has maintained a frenetic pace, traveling the world and performing political activities, as well as divorcing his second wife and marrying his third, the former fashion model and singer, Carla Bruni.
During his presidential campaign, Sarkozy pushed for greater transparency on presidential health bulletins, but his short hospital stay for a throat problem in 2007 was revealed only three months later.
Previous French presidents regularly concealed their health problems from the public.
The French public learned that former President Georges Pompidou had bone marrow cancer only after he died of it, while in office, on April 2, 1974.
Former President Francois Mitterrand, who led France from 1981-95 and died of prostate cancer just months after leaving office, ordered his doctor to systematically falsify his health bulletins for 11 years.
Former President Jacques Chirac was hospitalized for a week at Val de France in 2005 for a vascular problem and officials never fully explained what was wrong.
If a French president dies in office, the president of the Senate takes over temporarily while fresh presidential elections are organized.
Sarkozy is not the first president to have problems while jogging.
U.S. President Jimmy Carter was in the middle of a 10-kilometer race in Maryland when he collapsed into the arms of his bodyguards on Sept. 15, 1979. Dr. William Lukash said the next day that the American leader was in "excellent form."
By Associated Press Writer Deborah Seward