Brazilian shipping agency Williams said that the federal police and immigration inspectors have called a strike, which is set to begin this morning.
According to a Williams spokesman this strike action would seriously hamper movement of vessels approaching or leaving the nation's ports.
Brazil is one of the world's principal exporters of key agricultural produce including soy, coffee, sugar, ethanol, beef, chicken and orange juice.
If the strike does take place, Brazil's principal commodities ports of Santos and Paranagua are likely to be the first ones to be caught in possible congestion.