Leading article: Castro the younger's big step forward

Cuba is holding its first Communist Party Congress for 14 years. But it is a measure of the frenetic pace of developments elsewhere in the world and the low expectations that attach to set-piece gatherings in one-party states that it was not more keenly awaited. In the event, Raoul Castro produced a potentially epoch-making surprise. On the 50th anniversary of the speech by Fidel Castro that set Cuba on its communist course, his younger brother effectively declared it over.

In an address that could be as significant for Cuba as Nikita Khrushchev's denunciation of Stalin was for the Soviet Union, he said the party leadership needed renewal and that those in leading positions, himself included, should be limited to two five-year terms. He called on the party hierarchy to engage in severe self-criticism.

It will escape no one in Cuba that such change, if implemented, risks a period of turmoil that will filter down through every layer of power. It is also to be accompanied by a speeding-up of reforms in the economy, designed to reduce the role of the state and encourage small business. The tentative liberalisation announced last autumn seems to have been just the beginning. There is more to come, including the removal of state subsidies on many goods and a "rationalisation" of social spending. While President Castro insisted that Cuba would not deviate from its brand of socialism, one of the last hold-outs from the Cold War would appear to be on the brink of transformation.

A modernising, less inward-looking, Cuba should spell improvement – for its people's quality of life, as for the international atmosphere. But it will not be welcomed by all. Those with a stake in the system may resist reform, and some Cuban exiles in the US will be cynical about its feasibility, while fearing the loss of their own influence.

That it has taken Raoul Castro three years since assuming power to give this speech suggests the obstacles he may still face and the sensitivity of an eventual rapprochement with the US. In the end, the way the outside world can best speed change in Cuba is to avoid doing anything that might prompt its reversal.