BBC:
Cuba's ailing leader Fidel Castro has announced he will not return to the presidency, in a letter published by official Communist Party paper, Granma.
"I neither will aspire to, nor will I accept, the position of president of the council of state and commander in chief," he wrote in the letter.
Mr Castro handed over power temporarily to his brother, Raul, in July 2006 when he underwent intestinal surgery.
The 81-year-old has ruled Cuba since leading a communist revolution in 1959.
In December, Mr Castro indicated that he might possibly step down in favour of younger leaders, saying "my primary duty is not to cling to any position".
Soon afterwards, Raul Castro appeared to suggest that his older brother still had an important political role to play, saying the president still had full use of his mental faculties and was being consulted on all important policy issues.
Given his health these last couple of years, this should surprise no one. It will be interesting to note if the US-Cuba relations should manifestly change without Castro and how supportive the fairly influential Cuban-American community in Florida will be of making even a movement towards diplomatic relations with Cuba. Steve Clemons at The Washington Note looks at how the presidential candidates are likely to react.
