(Adds Nutrien mine shutdown plans, Cargill, farmer protest)
OTTAWA/MONTREAL, Nov 25 (Reuters) - A strike at Canada's largest railroad, Canadian National Railway Co., has forced one fertilizer company to set a date to curtail production and is threatening to slow agricultural exports with at least 30 vessels waiting at Canada's West Coast to load grain shipments.
As the strike by some 3,200 unionized employees entered its seventh day on Monday, labor union Teamsters Canada said it was no closer to an agreement than when the strike began.
Striking conductors and yard workers are demanding improved working conditions, including worker rest breaks in what is Canada's biggest rail strike in a decade.
Nutrien Ltd said on Monday it was preparing to shut down its largest potash mine, Rocanville, for two weeks effective Dec. 2 because of the CN strike.
Mark Hemmes, president of Quorum Corporation which monitors the movement of prairie grain for the Canadian government, told Reuters there were 21 ships parked in the Port of Vancouver as of Friday and nine anchored at the Port of Prince Rupert, in northern British Columbia.
Those figures, he added, were likely to rise by Monday to a combined 35 vessels, which are used to transport grains to international markets.
Canada relies on its two major railways - CN and Canadian Pacific Railway to move products like crops, oil, potash, coal and other manufactured goods to ports and the United States.
Economists have estimated a prolonged strike could hit already slowing growth expected by year's end while costing the Canadian economy billions of dollars. About half of the country's exports move by rail, industry figures show.
A CN spokesman said company officials continue to negotiate and call for binding arbitration, a demand the union has rejected thus far.
A spokeswoman for Canadian Labor Minister Filomena Tassi declined comment. The federal government has so far sidestepped calls to force employees back to work by insisting collective bargaining is the fastest way to solve the dispute.
The strike, Hemmes said, is affecting both shippers who are captive to CN lines and exporters who rely on CP, because many of the grain handling facilities at the country's major ports are serviced only by CN.
"Any Richardson facility or Cargill facility that is located on CP (lines) is basically unable to ship anything from the country to Vancouver," he explained, referring to major Canadian grain companies.
In a statement, Cargill Ltd. spokeswoman Connie Tamoto said the company had taken "mitigation measures" to ensure customer needs are met.
Richardson International could not immediately be reached for comment.
Around 300 farmers gathered with a dozen tractors near the prime minister's parliamentary office in Montreal on Monday to demand the government do more to end the strike because of a propane shortage.
CN is a key link in the transport of propane to parts of Eastern Canada where it is used to heat homes, hospitals, and to dry grain. Some farmers held bags of grain and signs that read "Propane - it's not just for barbecues" and "To dry grain, you need propane."
"Producers are increasingly distressed ... they are a bit exasperated by the government's lack of sensitivity so far," said Patrice Juneau of Quebec's Union of Agricultural Producers.
(Reporting by Kelsey Johnson in Ottawa, Allison Lampert in Montreal and Arunima Kumar in Bengaluru; additional reporting by Rod Nickel in Winnnipeg, David Ljunggren in Ottawa and Christinne Muschi in Montreal; Editing by Denny Thomas, Nick Zieminski and Chris Reese)