Raul Castro realises Cuba's communists "made real mistakes out of idealism", the BBC's Michael Voss reports from Havana. Cuban President Raul Castro has said top political positions should be limited to two five-year terms, and promised "systematic rejuvenation" of the government. President Castro was speaking at the start of the first congress of Cuba's ruling Communist Party in 14 years. He said the party leadership was in need of renewal and should subject itself to severe self-criticism. The proposal is unprecedented under Cuban communism. Mr Castro, 79, made clear the limits would apply to himself. He took over from his brother Fidel in 2008 and between them they have ruled Cuba for 52 years. He acknowledged that "the confidence of the majority of Cubans had been tested, with regard to the party and the revolution". Cubans, he said, would have to overcome a "mentality of inertia" and said the only thing that could threaten the revolution was "our inability to rectify errors". His brother and former leader Fidel Castro, now 84, missed the day's events. He said he regretted his absence but felt proud of the congress and the military parade that preceded it. Economic change In his speech, Raul Castro said the limit of two consecutive five-year terms would apply to "the current president of the Council of State and his ministers" - a reference to himself. Much of what he said concerned his plans to reduce the role of the state in the economy and encourage private enterprise. It would take at least five years to update Cuba's economic model, Mr Castro said. Free education and healthcare would still be guaranteed, but mass subsidies of basic goods would be removed and social spending would be "rationalised". Mr Castro said 200,000 people had already registered as self-employed since changes were announced last October, doubling the number of Cubans working for themselves. But he insisted the socialist character of Cuba would be "irreversible" and accumulation of property would not be allowed. The Communist Party Congress was preceded by a one of the largest military parades Cuba has seen in years, marking the 50th anniversary of the failed Bay of Pigs invasion by US-backed exile groups. Troops and armoured vehicles paraded through Havana's Revolution Square, followed by hundreds of thousands of civilians waving flags and chanting slogans. The parade and congress also celebrate 50 years since Fidel Castro proclaimed that his was a socialist revolution. In 1961, Cuban exile groups armed and trained by the American CIA came ashore at the Bay of Pigs, 100 miles (160 km) southeast of Havana, in an attempt to overthrow him. But after 72 hours of combat the invasion was defeated, in what Cuba celebrates as the "first great defeat for US imperialism in Latin America". Raul Castro, who is a general, donned military fatigues for the parade. There was no sign of Raul Castro's brother, the revolutionary leader and former President Fidel Castro, who is now 84 years old. But remarks attributed to him appeared later on the Cubadebate website, in which he spoke of a "feeling of pride" at the day's events. "It's worth to have lived to see that show today and it's worth always to remember those who gave their life to make it possible," he was quoted as saying. He said he could not have coped with the heat for more than an hour, but regretted being unable to attend. "Believe me, I felt myself ashamed when I saw some of you looking for me," he said. "I thought you would understand I can no longer do any more what I've done many times." The four-day party congress is expected to see 1,000 delegates back all or part of a package of nearly 300 reforms.