Quebec's supply of propane will run out within four days, threatening farmers' ability to dry their grain and heat their facilities, if a strike at Canadian National Railway isn't resolved soon, Premier François Legault said Thursday.

Legault described the situation as an "emergency" and called on federal opposition parties to be prepared to support back-to-work legislation.

The Alberta government has also asked Prime Minister Justin Trudeau to recall Parliament ahead of its scheduled return on Dec. 5 in order to legislate an end to the strike.

While Alberta's concerns involve stalled oil shipments, Legault is worried about Quebec's supply of propane, the vast majority of which is transported by rail from Sarnia, Ont.

"The strike cannot last," Legault said in an unprompted statement to journalists in Quebec City.

"Ideally, we hope for an agreement between the union and CN. But we can't rule out the need for a special bill in Ottawa."

Striking CN rail members outside the McLean Rail Yard in North Vancouver on Wednesday. Around 3,200 workers have been on strike since early Tuesday morning. (Jonathan Hayward/The Canadian Press)

On Wednesday, Quebec government officials began rationing the remaining 12 million litres of propane in the province.

The normal rate of consumption is six million litres per day, Legault said. With rationing, consumption will drop to 2.5 million litres per day.

He said the province is trying to find enough trucks to transport additional propane by road.

Rationing scheme put in place

Hospitals and seniors' residences will be prioritized in the rationing scheme, as will farmers, Legault said. Many were hit hard by the early snow and were relying on propane to dry out harvested grain.

Quebec Health and Social Services spokesperson Marie-Claude Lacasse told Radio-Canada in an email that although provincial health facilities use propane for heating, food preparation and other miscellaneous purposes, they have alternatives in place to deal with the propane shortage.

But the agricultural sector has been "severely impacted" by the propane rations, said Nathalie St-Pierre, president and CEO of the Canadian Propane Association.

Effectively cutting off propane access is compounding the wet grain issue, she said.

"Propane plays an important role in Quebec," St-Pierre said. "Propane supplies the fuel for 29 per cent of the activities in the agricultural sector, so it's a very important part of their requirements to deliver."

She added that 85 per cent of propane in Quebec is transported by rail.

William Van Tassel is a grain farmer in Quebec and a representative of the Quebec Grain Growers Association.

He said he finished harvesting and drying his grain a week ago, but he's spoken with other farmers who are concerned they could lose much of their crops.

"People are very nervous. Farmers are very nervous," he said.

The Canadian Propane Association is "urgently calling" on the government to meet to make sure Canadians are not left without heating fuels, St-Pierre said.

"When you depend on an infrastructure so important as the rail," she said, "it's difficult to have a plan B."

Grain Farmers of Ontario is also calling on the federal government to act.

Chair Markus Haerle says farmers can't face any more challenges this season and already need twice as much propane as they would in a normal year. If farmers don't receive propane, the financial impact will trickle down to what consumers pay, he says.

Legault warns NDP to support special law

Legault said he's been in touch with Trudeau's office, while other members of his government have reached out to federal Transport Minister Marc Garneau.

But Legault also singled out the New Democratic Party in his comments Thursday, suggesting it might be tempted to block back-to-work legislation because of the party's ties to unions.

"I wouldn't want the NDP, or another party, to decide to delay a special bill in order to please a union. You know how it is," Legault said.

Around 3,200 unionized CN workers went on strike early Tuesday. They're asking for improved working conditions, saying their long hours have become a safety concern.

They are also fighting against a lifetime cap on prescription drug coverage.