Unifor says workers at the St. Lawrence Seaway Corp. are ready to strike as of midnight Saturday.
It says it has issued a 72-hour strike notice to the employer and will bargain through Thursday in an attempt to reach a deal.
The union says a strike would effectively shut down transit through the seaway.
Negotiations began on June 19 and 20 with the help of a conciliator.
The two sides held additional talks in September and resumed bargaining on Oct. 17.
Unifor president Lana Payne says in a press release that workers are demanding a “serious wage offer.”