WINNIPEG, Manitoba (Reuters) - Port of Vancouver foremen will be locked out on Monday unless they scrap a proposed strike, employers at Canada's biggest port said on Friday, but grain handling would not be affected.

Canada's west coast ports are major outlets for the country's resource exports, including potash, coal, forestry products, pork and beef. A 13-day strike last year disrupted more than C$6 billion in trade at Vancouver and Port Rupert.

The British Columbia Maritime Employers Association said the proposed lockout of more than 700 foremen was preventative as the unit of the International Longshore and Warehouse Union representing them had already issued a 72-hour strike notice.

If the union withdraws the strike notice, Monday's lockout will not go ahead, the association said in a statement.

The two sides are in protracted talks over a labor deal and have been negotiating with the help of a federal mediator. The stoppage would also affect the port of Prince Rupert.

"In anticipation of escalating and unpredictable strike action, the BCMEA has made a decision to take defensive action in the form of a coastwide lockout," it said in a statement.

"It will not affect longshoring operations on grain vessels or cruise operations."

The association said the lockout notice has been issued in order to "facilitate a safe and orderly wind down of operations" in anticipation of a strike.

ILWU local 514 president Frank Morena said in a statement that it had only planned "limited job action" such as refusing overtime and accepting some technological changes, Canadian Press reported.

The impasse comes after a long-simmering dispute over pay and working conditions, including concerns over automation, with each side accusing the other of bargaining in bad faith.

The Port of Montreal, where workers are represented by the Canadian Union of Public Employees, saw the start on Thursday of a strike at two terminals operated by Termont, which handle 40% of the port's container traffic, but only 15% of its cargo.

Grain and other exports from the west coast were hit in August by a labor dispute at Canada's two major railways, which the federal government ended by imposing binding arbitration.

The government has resisted calls to interfere in collective bargaining in other disputes, other than offering mediation.

(Reporting by Ed White; Editing by David Ljunggren and Alexander Smith)

By Ed White