Farmers in Argentina's top farming province will halt sales of grain and livestock for four days to protest a planned tax rise, but exports should not be affected, an agricultural leader said on Monday.     

The protest in Buenos Aires province, starting on Thursday, could spread if provincial legislators vote to raise land taxes, said Julio Curras, vice president of the Argentine Agrarian Federation (FAA), adding that some growers say higher taxes could put them out of business.     

"It could lead to major protests all over the country," Curras said. Under the proposal, expected to be passed on Thursday, some farm tracts would be subject to rises of up to 350 per cent, the federation says.     

"It would make it impossible to work the land in a profitable way," the Argentine Rural Society (SRA), another prominent farm group, said in a recent statement.     

Argentina is the world's top supplier of soymeal, used as animal feed, and soyoil, used for cooking and in the booming international biofuels sector. It is also the world's number two supplier of corn and number three exporter of soybeans.

Buenos Aires province is Argentina's biggest producer of soybeans, corn and wheat.     

Farmer protests against soy export taxes disrupted grain exports in 2008 and 2009. Tensions had eased since then, although growers still complain about high soybean export taxes and government policy in the wheat and corn market.     

Labour unrest has surged in Argentina in recent years due to double-digit inflation.     

Near the main export hub of Rosario, oilseed-crushing workers grouped in the San Lorenzo branch of the main CGT labor federation said they would start blocking port terminals on Wednesday to press demands for a higher minimum wage.     

"If we don't have a deal with the crushing firms by Wednesday, we'll start the protest measures," said union representative Jose Aguirre. "It will be the same approach as last year - block the entrances of the biggest grains exporters."      

A protest by the same union slowed crushing in the Rosario area in November before the government ordered talks. – Reuters