In a letter dated February 18, ailing Cuban President Fidel Castro announced that he would not accept another term when the nation's new parliament meets on Sunday, effectively ending the rule of the 81-year-old Castro after almost 50 years in power, according to The Associated Press.

Castro's likely successor is believed to be his 76-year-old brother, Raúl. The president temporarily ceded power to his brother after undergoing intestinal surgery in July 2006.

"I will not aspire to nor accept — I repeat, I will not aspire to nor accept — the post of president of the council of state and commander in chief," reads the letter, signed by Castro and published early Tuesday in the online edition of the Communist Party daily, Granma. "My wishes have always been to discharge my duties to my last breath. That's all I can offer. ... It would be a betrayal to my conscience to accept a responsibility requiring more mobility and dedication than I am physically able to offer. This, I say, devoid of all drama."

Castro — who rose to power on New Year's Day 1959 and reshaped Cuba into a communist state — has not been seen in public since his operation, and has appeared only periodically in official photographs and videotapes. But since turning over power to his younger brother, he has published a number of essays, most with international themes.

Castro's announcement ends months of speculation that he'd renounce his office and comes just five days before his current mandate was set to expire. The news follows years-old claims that the fiery guerilla leader — who has survived several assassination attempts, the CIA-backed "Bay of Pigs" invasion of 1961 and efforts by the U.S. to topple him — was suffering from a terminal cancer. These reports have not been confirmed, nor have subsequent claims suggesting Castro was in "very grave" condition.

While the United States formulated a detailed plan three years ago to ensure a democratic transition following Castro's death, Cuban officials have long insisted the island's socialist political and economic systems would outlive the leader. His supporters have heralded his ability to provide a high level of health care and education for citizens while remaining fully independent of the United States. But Castro's detractors have painted him as a dictator whose totalitarian government systematically denied individual freedoms and civil liberties such as speech, movement and assembly.

Castro's brother, the AP reports, has raised expectations among Cubans for modest economic and other reforms. Last year, he said that Cuba required unspecified "structural changes" and acknowledged that government wages — which average about $19 a month — do not satisfy basic human needs.