President calls for reforms and limits on power in Cuba

Mr Castro said mistakes had left the country with no obvious successor.

The proposal for a limit of two five-year terms was made this weekend at the launch of a key Communist Party summit. It would make it all but impossible for a repeat of the Castros' own political dynasty, which has dominated Cuba since the 1959 revolution.

It would have little practical impact on Raul's future. The 79-year-old leader officially took over from his brother in 2008, meaning he wouldn't end his term in office until at least 2018, depending on how the law is written.

Mr Castro's proposals were made toward the end of a two-hour speech in which the Cuban leader forcefully backed a list of changes to the country's socialist economic system.

They included the eventual elimination of ration books and other subsidies, the decentralisation of the economy and a new reliance on supply and demand in some sectors.

He said that the party has made considerable progress on a study of whether to legalise the sale of cars and homes, which have been all but frozen since the revolution.

Mr Castro drew a line in the sand to illustrate the extent of the reforms, telling party luminaries that he had rejected dozens of suggested changes that would have allowed the concentration of property in private hands.

Mr Castro said the country had ignored its problems for too long and made clear Cuba had to make tough decisions if it wanted to survive. He said: "No country or person can spend more than they have. Two plus two is four. Never five, much less six or seven - as we have sometimes pretended."

Delegates to Congress will be splitting up into committees and meeting behind closed doors yesterday and today before Congress closes tomorrow.

Mr Castro alternated between reassurances that the economic changes were compatible with socialism, and a brutal assessment of the mistakes the country had made.

The Cuban leader said the monthly ration book of basic foods, perhaps the most cherished of subsidies, represented an "unbearable burden ... and a disincentive for work".

He said the changes he is proposing will come "without hurry, but without pause".

Mr Castro said he and his brother had made various attempts to promote young leaders, but that they had not worked out well - perhaps a reference to the 2009 firing of Cuba's photogenic foreign minister and vice-president, who were later accused of lusting too obviously for power. "Today we face the consequences of not having a reserve of substitutes ready," Mr Castro said.

Along with the proposals on economic changes, the two five-year terms idea does not yet carry the force of law since the party gathering lacks the powers of parliament. It is almost certain to be acted on quickly by the National Assembly.

The Communist Party is the only political organisation recognised on the island, and most politicians are members. Cubans vote for municipal and national assemblies, which in turn elect senior leaders including the president. Currently there is no set limit on their terms.

Since taking office, Mr Castro has leased tens of thousands of hectares of fallow government land to small farmers, and enacted reforms that allow Cubans to go into business for themselves, rent out homes and to hire employees.

Cubans are watching to see whether other changes emerge from Congress - such as the end of a near-total ban on buying and selling private property, or details on promises to extend bank credits.