Cuba, which built its socialist revolution on sugar cane production, plans to close almost half its sugar mills due to stagnant output and low world prices, official and diplomatic sources said Tuesday.

The Caribbean island will close 71 of its 156 state-run sugar mills in coming months as the communist government plans to restructure the uncompetitive industry, the sources said.

The mill closures were not expected to significantly affect Cuba's already depressed raw sugar production, though they will affect tens of thousands of workers and their families who have depended on the industry for generations.

"Everyone is very worried and sad, because this was our support for so many years," said Victoria Rodriguez, as she left the Pablo Noriega mill on bicycle for the last time.

The sugar mill where she worked for 20 years, 28 miles (45 km) south of Havana, shut down on Tuesday and the workers will be found jobs

elsewhere or retrained, Rodriguez said.

Authorities refused to comment on the closures, but official sources confirmed to Reuters they would take place now that the current sugar harvest is winding down.

"The decision was made earlier this year to definitively close 71 mills so we can put scarce resources into the most efficient mills and plantations," a mid-level official said.

"Many of the mills were temporarily closed during the last three or four harvests. Given low international sugar prices and our current financial problems it makes no sense to reopen them," he added.

The Cuban economy has depended on sugar exports for more than a century. Rum made from sugar is as much a part of the island's identity as its famous cigars.

After the 1959 revolution led by President Fidel Castro, masses of volunteers were mobilised each year to work in the fields cutting cane before harvesting was mechanised, and the government set a goal of reaching 10 million tonnes a year.