BARCELONA (Reuters) - Juan Antonio Samaranch, the 89-year-old former president of the International Olympic Committee (IOC), has been admitted to a Barcelona hospital with acute heart problems and is in a "grave situation."

Spaniard Samaranch, who was made the IOC's honorary life president when he stepped down in 2001, is on a respirator and undergoing an intensive programme of drug treatment, Rafael Esteban, director of internal medicine at the Quiron hospital, said at a news conference on Tuesday.

"At his age and with the chronic disruptions he is suffering we cannot be optimistic," Esteban said, adding that doctors had feared for Samaranch's life since his admission on Sunday.

"We cannot, at the moment, make any favorable prognosis," Esteban said.

Samaranch has suffered a number of health problems since his retirement and has been admitted to hospital several times.

He ran the IOC with absolute authority for two decades and Barcelona's successful bid to host the 1992 Olympics was seen as his personal triumph.

At last year's vote in Copenhagen on the host for the 2016 Games, he made an emotional appeal to IOC members to grant him a last favor and choose Madrid but Rio de Janeiro was picked.

"I know that I am very near the end of my time," Samaranch said during Madrid's final presentation.

He pursued a career in sports politics in dictator Francisco Franco's fascist Spain and won a place on the IOC in 1966.

After Franco's death, Samaranch was appointed ambassador to the Soviet Union and the contacts he made there helped him succeed Lord Killanin as IOC president in 1980.

He stepped down in July 2001, 21 years after he had been elected as the IOC's seventh president, and was made life president when he handed power to Belgian Jacques Rogge.

Shortly after, he spent 10 days in hospital in Lausanne and then two weeks in a clinic in Barcelona because of fatigue.

(Writing by Iain Rogers in Madrid, editing by Ed Osmond and Justin Palmer)