The federal government would have an obligation to end the Canadian Pacific rail strike if it began hurting the national economy, Labour Minister Lisa Raitt declared on Thursday as companies worked to survive without freight service.

About 4,800 Canadian Pacific Railway workers walked off the job early Wednesday after reaching a midnight strike deadline without having reached a deal with the employer.

Freight service ground to a halt, and on Wednesday CP temporarily laid off 2,000 additional workers whose services they say aren't needed during the stoppage. Another 1,400 employees could also be sent home at any time, the company said.

The strike has suspended freight shipments across the country, affecting the oil and coal industries as well as automotive, fertilizer and lumber shipments, to name a few.

Raitt told CTV's Canada AM on Thursday that a negotiated settlement is the best solution, but said the federal government is ready to step in if that doesn't happen. Raitt estimates a prolonged strike will cost the Canadian economy $540 million per week.

"When 5,000 employees going on strike starts affecting tens of thousands of employees at Ford plants or GM plants or at coal mines or grain farmers, then it's a bigger impact than what's just happening at the company," Raitt said.

"And it's more than appropriate, in fact one would say the government is obliged to step in and ensure we put the people back to work and we make sure the system continues to operate for the greater sake of the nation."

With the CP strike winding through its second day, companies across Canada were forced to search out Plan B options to deal with the lack of freight transportation.

Cenovus Energy Inc. relies on CP Railway to transport about 2,000 barrels of oil every day (a small fraction of its 156,850 daily output), and says it is working to secure extra pipeline capacity to move its product.

Producers in other industries are not as lucky. Fertilizer and mining companies rely almost exclusively on train shipments. Some potash trains can stretch two kilometres in length. It would take two and a half trucks to replace a single train car, according to a spokesman for the Canadian Fertilizer Institute.

Bill Boyd, Saskatchewan's minister of energy and resources, joined the call for an end to the rail strike, writing a letter to Raitt on Thursday and urging a quick resolution.

"CP's rail network is critical in moving Saskatchewan grain, oil, timber and minerals to markets all over the world," Boyd wrote, according to The Canadian Press.

"Without this connection, jobs and investment are at significant risk, and so is our international reputation as a reliable supplier of valuable products."

On Wednesday, Raitt put CP Rail and its striking workers on notice that the government was preparing legislation and was ready to act if the union and employer can't reach a deal on their own. On Thursday, however, she said the government is giving the parties some space to work out their own agreement.

"They're at the table again this morning starting at 9 o'clock and they were at the table last night, and they have the ability to do their own deal and that's really what we're focusing on right now," she said.

Raitt has intervened in recent labour disputes at Air Canada and Canada Post, using the justification that a work stoppage would harm the economy and inconvenience Canadians.

MPs are on break this week, and the government would have to call them back for an emergency session of Parliament if it wanted to introduce back-to-work legislation earlier than Monday.

Raitt has not indicated she would make such a move.

The opposition decried the government's move to have back-to-work legislation at the ready. NDP labour critic Alexandre Boulerice called it an "attack against the rights of workers to associate and to freely negotiate."

He also said it takes the pressure off CP during negotiations.

Ahead of the labour disruption Wednesday, both sides said commuter trains in Montreal, Vancouver and Toronto that use CP rail lines would continue to shuttle passengers to work and back, regardless of the strike.

However, a Via Rail route between Sudbury and White River, and the section of the Toronto-to-Ottawa route between Brockville and Ottawa are affected. Via said it is moving passengers by an alternate form of transportation along those routes.

At odds over pensions, benefits

Canadian Pacific is seeking changes to its legacy pension plan and retirement benefits model, saying the changes are necessary for the railway to remain competitive.

CP said it has offered a pension plan that is a "multiple" of the average industrial pension in Canada and exceeds an agreement the teamsters reached "at another major Canadian railway."

The union is fighting to maintain its pension and protect fatigue management measures for workers.

In total, the Teamsters Union represents 125,000 members in Canada across all trades.