The state-run Granma newspaper quotes President Raul Castro as saying party leaders are analyzing the economy to determine, in his words, "what must be perfected and even eliminated."
The congress, which last gathered in 1997, was scheduled to meet late this year in order to set a long-term course for Cuba's future.
The congress was expected to consider Cuba's future for long after President Castro, and his older brother and former President Fidel Castro, are gone. Elections also were expected to be held to fill key Communist Party positions.
The postponement comes as Granma reports that the island nation's 2009 economic growth forecast has been lowered by nearly one percentage point, from 2.5 to 1.7 percent.
Agencies