MONACO — Groomed from birth to rule, Prince Albert took over Monaco's royal powers yesterday, assuming all but the throne in the tiny principality after a royal commission decided his critically ill father is too sick to perform his duties.

The announcement by the royal palace marked the first time since 1949 that Prince Rainier III — Europe's longest-serving ruler — has not been in control of the Mediterranean realm smaller than New York's Central Park and famed as a playground for the rich and famous.

Albert, 47, is the only son of Rainier and his late wife, Grace Kelly, the American beauty who exchanged Hollywood stardom for the life of a princess.

Well-traveled, multilingual and Monaco's top ambassador in recent years, the unmarried Albert is also regarded as a shy, even reluctant, heir. Sports are a love: He is a five-time bobsledding Olympian and has headed Monaco's Olympic committee since 1994.

Albert promised to devote himself "with strength, conviction and passion" to his new role as regent.

Rainier, 81, was hospitalized March 7 and has been in intensive care for 10 days with breathing, kidney and heart problems.

Albert has been groomed to rule the principality that has been run by his family — the Grimaldis — for seven centuries.

But he has remained heirless — causing so much concern that the constitution was revised in 2002 to ensure the continuation of the dynasty. His older sister — Princess Caroline, now 48 — would succeed him. She in turn, would be succeeded by her oldest son, Andrea Albert Pierre, 20.

Albert studied in the United States, at Amherst College in Massachusetts, after receiving his high-school baccalaureate diploma in 1976. He returned home in 1981 after being awarded a degree in political science.