HAVANA - Cuban President Raul Castro called for handing over power to the younger generations on Tuesday in an address at the closing of the 7th Congress of the Cuba's Communist Party (PCC).

Castro signaled that he wants top leaders to retire at 70, starting from 2021, and that the next five years would be a transition period for creating a younger generation of leaders.

Castro, who was elected first secretary for a second term, thanked the PCC Congress but said the current congress would be the last led by leaders of the 1959 Revolution.

"Due to the inexorable law of life, this Congress will be the last led by the historic generation, who will hand over the flags of revolution and socialism to its younger pillars, without sadness or pessimism," Castro said in presence of Fidel, almost 1,000 delegates and around 280 guests.

The president, 84, said that the PCC's main mission must be "to defend, preserve and continue perfecting socialism and never allowing the return of capitalism."

"I will dedicate my time to the reform process of the Constitution to make the necessary changes, after 40 years of its existence," said Castro.

Castro has served as first secretary of the PCC since the last congress in 2011, when he officially replaced his brother, Fidel, the revolutionary leader who left active political life due to health reasons. The presidency of Raul Castro is expected to end in 2018.

The PCC has transformed the island country, leading to a prosperous, sustainable and irreversible socialism, with the Revolution's principles of justice and equality enshrined, Castro said.