In a 2-hour speech Saturday to 1,000 delegates at the opening of the Sixth Communist Party Congress, the 79-year-old said the party needs to become more current and focus on grooming new leaders while limiting terms, The New York Times reported.
"We have arrived at the conclusion that it is advisable to limit the fundamental political and state offices to a maximum period of two consecutive periods of five years," Castro said.
If that is imposed, Castro would have to step down in 2018.
He repeatedly affirmed his loyalty to socialism and free healthcare and education, but said parts of the old Cuban model were economically unsustainable, such as food ration coupons.
"No country or person can spend more than they have," Castro said. "Two plus two is four. Never five, much less six or seven, as we have sometimes pretended."
Last year, Castro shocked the country by announcing the layoffs of 500,000 government workers representing 80 percent of the entire labor force. However, earlier this month he said he was delaying the job cuts indefinitely, the report said.
The party congress concludes Tuesday.