The Canadian Coast Guard says it is sending more icebreakers to help clear shipping channels in the frozen Great Lakes and St. Lawrence Seaway.
Faced with the worst ice conditions in 20 years, the coast guard says it is too early to say when freighters filled with grain and other commodities will be able to move normally through the trade corridor.
The seaway is to officially open between Lake Ontario and Montreal on March 31, but ice conditions west of that area are extreme.
Mario Pelletier, the coast guard's assistant commissioner, says two additional icebreakers and a hovercraft will help clear ice by early next week.
The Canadian Shipbuilders Association has said a lack of icebreakers would delay shipments of Prairie grain and other goods including iron ore, construction materials and petroleum products.
The coast guard says its ships are working full-out, but weather conditions will affect how quickly the shipping channels can be cleared of ice.