Cuban soldiers and hundreds of thousands of civilians parade to commemorate the 50th anniversary of the failed Bay of Pigs invasion along the Plaza de la Revolucion Havana on Saturday. Miguel Guzman/Associated Press

Raul Castro proposed term limits for Cuban politicians — including himself — on Saturday, a remarkable gesture on an island ruled for 52 years by him and his brother.

The president, 79, lamented the lack of young leaders in government, saying the country was paying the price for errors made in the past. He told delegates to a crucial Communist Party summit in Havana that he would launch a "systematic rejuvenation" of the government.

Castro said politicians and other important officials should be restricted to two five-year terms, including "the current president of the Council of State and his ministers." He holds that title.

Castro officially took over from his brother Fidel in 2008, meaning he would be at least 86 when his second term as Cuban leader ended, depending on how the law is written.

Some economic changes endorsed

Cuban soldiers march at the Plaza de la Revolucion, or Revolution Square, as part of Saturday's festivities. President Raul Castro was expected to announce significant reforms to Cuba's economy. Javier Galeano/Associated Press

The proposal was made during the latter stage of a 2½-hour speech in which the Cuban leader forcefully backed a laundry list of economic changes to the country's socialist system, including the eventual elimination of the ration book and other subsidies, the decentralization of the economy and a new reliance on supply and demand in some sectors.

Still, he drew a line at some proposed changes, telling party luminaries that he had rejected dozens of suggested reforms which would have allowed the concentration of property in private hands.

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.

"No country or person can spend more than they have," he said. "Two plus two is four. Never five, much less six or seven — as we have sometimes pretended."

Dressed in a white guayabera shirt, the Cuban leader alternated between reassurance that the economic changes were compatible with socialism, and a brutal assessment of what has not worked in the past.

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

Still, he said, in Cuba "there will never be room for shock therapy."

Of the term limits, 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.

"Today we face the consequences of not having a reserve of substitutes ready," Castro said.

As with the proposals on economic changes, the term-limit idea does not yet carry the force of law since the party gathering lacks the powers of parliament. But it is all but certain to be acted on quickly by the national assembly.

Fidel Castro was not present for the speech, but a chair was left empty for him near his brother.

Parade marks Bay of Pigs battle

Cuba kicked off the congress with a big military and civilian parade to mark 50 years since the defeat of CIA-backed exiles at the Bay of Pigs, still celebrated as a landmark triumph over the island's powerful neighbour to the north.

Thousands of soldiers high-stepped through sprawling Revolution Plaza as a military band played martial music, not far from an iconic sculpture of Ernesto (Che) Guevara that gazes down from the side of the Interior Ministry building. Helicopters whirred and jet fighters in combat formation roared overhead while freshly painted amphibious assault vehicles and rocket launchers rumbled past.

"Long live Fidel! Long live Raul! Long live the Communist Party of Cuba!" a female announcer shouted, and participants responded with shouts of approval.

Tweaking a theme from Abraham Lincoln's Gettysburg Address, a male announcer declared Cuba's revolution to be "Of the humble, by the humble, and for the humble."

Raul Castro donned military fatigues for the occasion. He looked on with other dignitaries from a dais, waving and saluting the troops.

Hundreds of thousands of Cubans — from aging veterans to factory workers — took part, many ferried to the plaza on a fleet of aging Soviet-era buses and some shiny new ones purchased from China, leaving the rest of the city mostly deserted.