It’s official; Fidel Castro has resigned as Cuba’s president.

HAVANA - An ailing, 81-year-old Fidel Castro resigned as Cuba’s president Tuesday after nearly a half-century in power, saying he will not accept a new term when parliament meets Sunday.

The end of Castro’s rule — the longest in the world for a head of government — frees his 76-year-old brother Raul to implement reforms he has hinted at since taking over as acting president when Fidel Castro fell ill in July 2006. President Bush said he hopes the resignation signals the beginning of a democratic transition.

“My wishes have always been to discharge my duties to my last breath,” Castro wrote in a letter published Tuesday in the online edition of the Communist Party daily Granma. But, he wrote, “it would be a betrayal to my conscience to accept a responsibility requiring more mobility and dedication than I am physically able to offer.”

In the pre-dawn hours, most Cubans were unaware of Castro’s message, and Havana’s streets were quiet. It wasn’t until 5 a.m., several hours after Castro’s message was posted on the internet, that official radio began reading the missive to early risers.

By sunrise, most people headed to work in Havana seemed to have heard the news, which they appeared to accept without obvious signs of emotion. There were no tears or smiles as Cubans went about their usual business.