OTTAWA, Aug 9 (Reuters) - The Canadian Teamsters union,

which is negotiating a contract with the country's two largest

rail companies, on Friday said a work stoppage could start on

Aug. 22 if a deal is not reached.

"The Teamsters will provide 72 hours advance notice in the

event of any strike action," it said in a statement.

The union, Canadian National Railway ( CNI ) and Canadian

Pacific Kansas City ( CP ) agreed last week to restart stalled

contact talks with the aid of a federal mediator.