The Canadian Union of Postal Workers has given 72-hour strike notice to Canada Post.
The notice is for both the union's urban and rural bargaining units.
In a release early Tuesday morning, the union says workers will be in a legal strike position as of Friday if negotiated settlements have not been reached.
However, the union says its national executive board has yet to decide if a job action will happen at the deadline, saying that will depend on Canada Post's actions at the bargaining table in the coming days.
CUPW Windsor Local 630 represents around 520 workers at sites at the main sorting plant on Walker Road, two city depots, the Rural & Suburban Mail Carrier office on Patillo Road and at a retail location downtown.
CUPW Windsor Local 630 President Tish Glenn says wages and safe working conditions are among the concerns of her members locally.
"And of course work-life balance has been taken away from these folks. We have new start times that have been put into place and implemented, and they're very late start times, starting anywhere from 10 a.m. going to the upwards of 11:30 a.m. for letter carriers to start their routes, and the right to retire with dignity."
She says a strike would potentially stop the flow of mail.
"I need folks to understand this isn't the postal workers that have put this situation in place, it's the fact that we're trying to negotiate at the table in good faith, and that's not happening, and that's why we're in the position we are right now."
Glenn says Canada Post must listen to workers who are on the ground working, who know the job the best.
"What Canada Post has offered postal workers at the bargaining table is anti-worker. It's plain and simple. No union in the world would ever consider accepting the proposed rollbacks that we're being given."
The union rejected Canada Post's latest contract offer that included annual wage increases that amounted to 11.5 per cent over four years.
It also offered protection of the defined benefit pension for current employees, as well as job security and health benefits.