Argentina is one of the world's biggest exporters of soya
Farmers in Argentina say they will resume protests against tax increases on food exports, following the collapse of talks with the government.
Farm leaders say they plan to prevent shipments of grain from leaving.
Argentina is one of the world's top exporters of corn, wheat, soya and beef.
Correspondents say a prolonged dispute could have an impact on international markets at a time when food prices are already at record levels.
The farmers are particularly angry about an increase to the export tax on soya - a commodity which last year earned the country $13bn (£6.6bn).
In March protesting farmers blocked roads for three weeks, preventing trucks from delivering produce, leading to food shortages.
Road of confrontation
Several weeks of negotiation have ended without agreement, and the farmers said they would resume the protests, although they promised not to block highways, as they did in the previous strike.
"After 57 days, we haven't advanced," said Eduardo Buzzi, president of the Argentine Agrarian Federation.
"The government has chosen the road of confrontation. It's the only reason we haven't reached an agreement," he added.
President Cristina Fernandez de Kirchner has said the taxes are a means to raise badly-needed revenue, curb inflation and guarantee domestic supplies.
The BBC's Daniel Schweimler in Buenos Aires says the March protests threw the country into disarray, and plunged the government into crisis.
The economy minister, Martin Lousteau, was sacked over the crisis.