Cuban President Raul Castro has postponed the first congress of the ruling Communist Party since 1997.
Mr Castro said the congress, which was expected before the end of the year, was being delayed so the party could deal with escalating economic problems.
He was quoted as saying the economic situation was "very serious".
Cuba has lowered its projected economic growth estimate for this year from 2.5% to 1.7% - down from an initial estimate of 6%.
In the past, the congress set Cuba's economic and political direction, and elected party leaders.
The BBC reports the one planned for this year was set to chart the country's future into an era where the generation that led the Cuban revolution is no longer in charge.
Mr Castro, 78, formally took over last year from his brother Fidel, who had led Cuba since taking power in the revolution of 1959.
The congress was due to decide whether Fidel Castro, 82, would continue as head of the party. He stepped aside after undergoing gastric surgery in 2006 and has largely retreated from public life.