ST. CATHARINES, Ont. - The St. Lawrence Seaway has averted a strike that could have crippled one of North America's busiest shipping routes.

The tentative agreement was reached ahead of a noon strike deadline on Monday and after the union gave its 72-hour strike notice on Friday.

The Canadian Auto Workers union says it turned back key concession demands by the St. Lawrence Seaway and is unanimously recommending members approve the three-year agreements by five locals.

"We've negotiated economic improvements as well as improvements to other structural sections of the collective agreement," CAW national representative Mike Menicanin said in an interview.

He said the seaway backed down from key demands concerning pension plans for new hires and health premiums.

It wanted new hires to be subject to defined contribution rather than defined benefit pension plans. It also initially demanded workers pay a portion of health premiums that would have cost the average worker $170 per month, he said.

Terms of the three-year collective agreements for three locals will be disclosed after workers vote on them in the coming 10 to 12 days.

Terence Bowles, president and CEO of the St. Lawrence Seaway Management Corp., said the deal "will allow ships to continue transiting the waterway without interruption."

The private, not-for-profit company had said Friday that the Seaway would be closed to all traffic in the event of a strike.

The Seaway serves some of the most important industrial cities in Canada and the U.S. and provides a route for the export of grain and other commodities.

It also allows for large freight ships to travel between the Atlantic Ocean and the five Great Lakes -- serving some of the most important industrial cities in Canada and the U.S. and providing a route for the export of grain and other commodities.

The Seaway is also highly sensitive to competition from numerous other options, including the trucking industry and various other ports on the East Coast.

The management company is responsible for the movement of marine traffic through the Canadian Seaway facilities, which includes 13 of the 15 locks that lift and lower ships between Montreal and Lake Erie.

In Ottawa, Labour Minister Lisa Raitt applauded the tentative agreement that averted the seaway's first strike in 43 years.

"Negotiated agreements are in the best interest of the organization, employees, businesses and the Canadian economy," she said in a new release.

With the global economy still being very fragile, she said the government was committed to protecting Canada's economy and Canadian jobs.

Last week, Raitt threatened back to work legislation as she had with two unions at Air Canada earlier this year, and legislated striking Canada Post workers back to work, citing the impact that the job actions would have on the economy.

Although the agreement won't necessarily please all members, Menicanin said it was a good deal in the face of the intervention of the federal government.

Menicanin said the intervention was a distraction but had no impact on negotiations or the deal reached.

He said the union was "flabbergasted" by the "bombs" dropped by the minister.

"Once we got over this unwanted complication, we got back to the task at hand and that was try and settle a contract, which we have been doing quite successfully for over 40 years without the help of the minister of labour."

The CAW represents 475 supervisory, operations, maintenance and headquarters workers in at the corporation in Ontario and Quebec.

The two sides began negotiating three collective agreements in May and the latest round of negotiations began Sept. 19.