BUENOS AIRES, April 24 (Reuters) - A union of Argentine transporters on Monday ended a strike that was posing a threat to the country's grains shipments, local agriculture exporters groups said.

The transporters began the strike Monday morning, raising concerns over activity at the Rosario agro-port hub and forcing exporters to rely on dwindling grain reserves at the terminals.

The country's government and the union signed a memorandum of understanding with the commitment to lift any measure of force in place, within the framework of a "table for dialogue and social peace," the transportation ministry said in a statement.

The Single Freight Carriers Union (Siunfletra), which brings together truck owners, had been asking for an increase in the tariffs on the transportation of merchandise and for a seat at the table at the meeting where these rates are decided.

The ministry added it would work on a policy "that establishes that the tariff schemes, which to date have an indicative nature, become floor or base tariffs and that they would be mandatory for the suppliers."

Earlier, transporters prevented the passage of trucks carrying grains in the province of Santa Fe, where the Rosario terminals are located, practically paralyzing the entry of vehicles to one of the largest export centers in the world.

In Argentina, more than 80% of grain transportation is done with cargo trucks.

"The transport of land cargo is in an emergency. The rates are derisory. You can't cover the costs of the truck, you don't have profitability," said Daniel Seanopolo, a representative of the port branch of Siunfletra.

Argentina's corn and soybean harvest, which has been hit by an intense drought, has just begun, meaning traffic is usually intense at this time of year in Argentina.

A source from the chamber of grain exporters and processors (CIARA-CEC) said that shipments remained steady on Monday despite the strike. (Reporting by Maximilian Heath; Additional reporting by Jorge Otaola; Writing by Valentine Hilaire Editing by Marguerita Choy and Lincoln Feast)