Grain prices spiked last week as more than 150 grain-laden vessels lay idle outside Argentina's ports and along the Uruguayan coast but neither side appeared nearer a compromise.
Dockworkers' representatives warned Fernandez they would launch a general strike unless the government met their demands for improved wages and easier taxation rules.
The work stoppages sent shock waves through the soy meal trade, which is central to international supplies of animal feed, soy oil production and a growing biofuels energy sector.
Worried traders also predicted worsening prospects for soybeans and corn trade because of the Latin American country's leading position in those two grain markets. Argentina is the world's third largest supplier of soybeans and the No. 2 corn exporter after the United States.
Port authorities received a tongue-lashing from the dockworkers' representatives after they announced -- prematurely -- a work stoppage had ended and the dockworkers had gone back to work.
Dockworkers' union leader Omar Suarez denied members had returned to work and vowed to prevent ships from entering or leaving the harbor at Rosario, the country's main grain hub.
The union says dockworkers' work shifts are understaffed, forcing those called on duty to perform extra tasks and sometimes work longer hours.
The dockworkers' discontent has combined with farmers' protests and teachers' strikes to inject new uncertainties in Argentine economy and society.
So far the labor leaders have said a general strike would be a last resort but warned that government inaction may push them toward calling for countrywide industrial action.
"I hope we don't come to call for a general strike," CGT labor union leader Hugo Moyano told reporters. "I hope we're not pushed to call for a general strike."
At the heart of the dispute is the government's interpretation of the cost of living, the rate of inflation and consumer price index in Argentina. Government statistics of inflation and the consumer price index are generally believed to be about a third of the actual trends -- currently said to exceed 25 percent.
The government has also attracted the teachers' ire after Fernandez claimed the teachers worked too few hours -- four hours a day, one of her comments alleged -- and claimed long vacations.
The labor unions' representations have backed the teachers' demands and urged the government to be "reasonable" in its approach to various sections of Argentina's work force.
Nowhere is the threat to the economy more pronounced than in the ports, where traders fret over millions of dollars of grain trade at risk from the prolonged dispute.