The Canadian Coast Guard says it is sending more icebreakers to help clear shipping channels in the frozen Great Lakes and St. Lawrence Seaway.

"What we have committed to do given the extreme conditions is to bring two more assets (icebreakers), as well as a hovercraft, to facilitate the opening of the seaway," Mario Pelletier, the coast guard's assistant commissioner, said from Ottawa Wednesday.

Faced with the worst ice conditions in 20 years, Pelletier said 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 Canadian Shipbuilders Association said Tuesday that a lack of icebreakers would delay shipments of Prairie grain and other goods including iron ore, construction materials and petroleum products from ports such as Thunder Bay, Ont.

A section of the seaway between Lake Ontario and Montreal is frozen but it set to open March 31.

Shipping channels west of that area are choked with thick ice.

"The conditions at Thunder Bay and the Sault Ste. Marie system is very extreme and the eastern portion of Lake Erie," Pelletier said.

There are already two coast guard icebreakers in the Great Lakes.

One additional icebreaker is to be in the seaway system by Friday, Pelletier said.

It is to be joined by another icebreaker and a hovercraft early next week. More coast guard ships could follow.

Pelletier said the coast guard should have a better idea of the challenge it faces once these additional ships are on the job.

"The next week will be critical," he said.

Pelletier said the icebreakers will help move some of the freighters through the ice in convoys.

The shipbuilders association, which represents six companies that control 83 freight vessels, has said it doesn't believe normal shipments will be achieved until mid April.

It contends the coast guard doesn't have enough icebreakers to meet demand and that many of the ships it has are getting old.

Association president Robert Lewis-Manning said the coast guard announcement of more icebreakers is welcome, but said another ship is needed to help free up the ice-clogged shipping lanes.

"I think it is a positive approach and hopefully, if conditions will allow for it, they will bring in another icebreaker as well," he said.

Pelletier said the ships and crews are working full-out, but weather conditions will affect how quickly the shipping channels can be cleared of ice.

He said the seaway system, which is jointly operated by Canada and the U.S., was not built to be efficient under extreme conditions.

Pelletier acknowledged the coast guard fleet is getting old, with some ships nearing 30 years of service. He said there is a program underway to upgrade ships and extend their operational life.

"It is the worst ice year we have had in 20 years. For an average year we do have enough icebreakers," he said.

"We do have the right mix of assets to respond to the task. This year has to be looked at as an exceptional year."

The Manitoba government and some Prairie farm groups have said they hope more grain from the recent bumper crop that has been sitting in storage due to the rail transportation backlog could be shipped by freighters through the Great Lakes.