As back-to-work legislation forced the end of rotating strikes by Canada Post workers, the agency is warning customers to expect “lengthy delays” for some types of deliveries.

In a notice on its website, Canada Post said parcel deliveries will continue, but will be delayed “during the peak holiday season and into January, 2019.”

“Existing backlogs are expected to worsen this week due to high volumes from Black Friday and Cyber Monday sales,” the notice said.

If you’re expecting a parcel from another country, internationally shipped items may experience delays stretching into March, 2019, Canada Post said.

The agency said it is working with the Canada Border Services Agency, which screens the packages, “to manage the significant existing backlog.”

The letter mail backlog “should be cleared and deliveries current before Dec. 25,” Canada Post said.

Even though Canada Post workers have been legislated back to work, the Canadian Union of Postal Workers has told its members that it will soon begin a campaign of "mobilizations, demonstrations and non-violent civil disobedience."

CUPW national president Mike Palecek told CTV’s Power Play on Tuesday that “all options are on the table.”

“Over the coming days, you’re going to see actions unfolding.”

Palecek said there’s “no such thing as good back-to-work legislation,” and called the current law passed by the House of Commons and the Senate “unconstitutional.”

“Let’s be clear – it will not be business as usual at the post office,” Palecek told Power Play host Don Martin. “You cannot legislate labour peace. You can only negotiate it.”